Apple shares rose 13% this week, its largest weekly gain in more than five years, after CEO Tim Cook appeared with President Donald Trump in the White House on Wednesday.

Shares of the iPhone maker rose 4% to close at $229.35 per share on Friday for the company’s largest weekly gain since July 2020. The week’s move added over $400 billion to Apple’s market cap, which now sits at $3.4 trillion.

Apple is the third-most valuable company, behind Nvidia and Microsoft and ahead of Alphabet and Amazon.

At the White House on Wednesday, Cook appeared with Trump to announce Apple’s plans to spend $100 billion on American companies and American parts over the next four years.

Apple’s plans to buy more American chips pleased Trump, who said during the public meeting that because the company was building in the U.S., it would be exempt from future tariffs that could double the price of imported chips.

Investors had worried that some of Trump’s tariffs could substantially hurt Apple’s profitability. Apple warned in July that it expected over $1 billion in tariff costs in the current quarter, assuming no changes.

“Apple and Tim Cook delivered a masterclass in managing uncertainty after months and months of overhang relative to the potential challenges the company could face from tariffs,” JP Morgan analyst Samik Chatterjee wrote on Wednesday. He has an overweight rating on Apple’s stock.

Cook’s successful White House meeting also comes two weeks after Apple reported June quarter earnings in which overall revenue jumped 10% and iPhone sales grew by 13%.

WATCH: Santoli’s Last Word: Apple helps drive S&P higher

Tesla has been granted a permit to run a ride-hailing business in Texas, allowing the electric vehicle maker to compete against companies including Uber and Lyft.

Tesla Robotaxi LLC is licensed to operate a “transportation network company” until August 6, 2026, according to a listing on the website of the Texas Department of Licensing and Regulation, or TDLR. The permit was issued this week.

Elon Musk’s EV company has been running a limited ride-hailing service for invited riders in Austin since late June. The select few passengers have mostly been social media influencers and analysts, including many who generate income by posting Tesla fan content on platforms like X and YouTube.

The Austin fleet consists of Model Y vehicles equipped with Tesla’s latest partially automated driving systems. The company has been operating the cars with a valet, or human safety supervisor in the front passenger seat tasked with intervening if there are issues with the ride. The vehicles are also remotely supervised by employees in an operations center.

Musk, who has characterized himself as “pathologically optimistic,” said on Tesla’s earnings call last month that he believes Tesla could serve half of the U.S. population by the end of 2025 with autonomous ride-hailing services.

The Texas permit is the first to enable Tesla to run a “transportation network company.” TDLR said Friday that this kind of permit lets Tesla operate a ride-hailing business anywhere in the state, including with “automated motor vehicles,” and doesn’t require Tesla to keep a human safety driver or valet on board.

Tesla didn’t immediately respond to a request for comment.

As CNBC previously reported, Tesla robotaxis were captured on camera disobeying traffic rules in and around Austin after the company started its pilot program. None of the known incidents have been reported as causing injury or serious property damage, though they have drawn federal scrutiny.

In one incident, Tesla content creator Joe Tegtmeyer reported that his robotaxi failed to stop for a train crossing signal and lowering gate-arm, requiring a Tesla employee on board to intervene. The National Highway Traffic Safety Administration has discussed this incident with Tesla, a spokesperson for the regulator told CNBC by email.

Texas has historically been more permissive of autonomous vehicle testing and operations on public roads than have other states.

A new law signed by Texas Republican Gov. Greg Abbott goes into effect this year that will require AV makers to get approval from the state before starting driverless operations. The new law also gives the Texas Department of Motor Vehicles the authority to revoke permits if AV companies and their cars aren’t complying with safety standards.

Tesla’s AV efforts have faced a number of challenges across the country, including federal probes, product liability lawsuits and recalls following injurious or damaging collisions that occurred while drivers were using the company’s Autopilot and FSD (Full Self-Driving) systems.

A jury in a federal court in Miami last week determined that Tesla should hold 33% of the liability for a fatal Autopilot-involved collision.

And the California DMV has sued Tesla, accusing it of false advertising around its driver assistance systems. Tesla owners manuals say the Autopilot and FSD features in their cars are “hands on” systems that require a driver ready to steer or brake at any time. But Tesla and Musk have shared statements through the years saying that a Tesla can “drive itself.”

Since 2016, Musk has been promising that Tesla would soon be able to turn all of its existing EVs into fully autonomous vehicles with a simple, over-the-air software update. In 2019, he said the company would put 1 million robotaxis on the road by 2020, a claim that helped him raise $2 billion at the time from institutional investors.

Those promises never materialized and, in the robotaxi market, Tesla lags way behind competitors like Alphabet’s Waymo in the U.S. and Baidu’s Apollo Go in China.

Tesla shares are down 18% this year, by far the worst performance among tech’s megacaps.

WATCH: What we saw at Tesla’s robotaxi launch in Texas

Shares of The Trade Desk plummeted almost 40% on Friday and headed for their worst day on record after the ad-tech company announced the departure of its CFO and analysts expressed concerns about rising competition from Amazon.

The Trade Desk, which went public in 2016, suffered its steepest prior drop in February, when the shares fell 33% on a revenue miss. In its second-quarter earnings report late Thursday, the company beat expectations on earnings and revenue, but the results failed to impress investors.

The Trade Desk, which specializes in providing technology to companies that want to target users across the web, said finance chief Laura Schenkein is leaving the job and being replaced by Alex Kayyal, who has been working as a partner at Lightspeed Ventures.

While some analysts were uneasy about the sudden change in the top finance role, the bigger concern is Amazon’s growing role in the online ad market, as well as the potential impact of President Donald Trump’s tariffs on ad spending.

Amazon has emerged as a significant player in the digital advertising market in recent years, and is now third behind Google and Meta. Last week, Amazon reported a 23% increase in ad revenue for the second quarter to $15.7 billion, which beat estimates.

Amazon’s ad business has largely been tied to its own platforms, with brands paying up so they can get discovered on the sprawling marketplace. However, Amazon’s demand-side platform (DSP), which allows brands to programmatically place ads across a wider swath of internet properties, is gaining more resonance in the market.

“Amazon is now unlocking access to traditionally exclusive ‘premium’ ad inventory across the open internet, validating the strength of its DSP and suggesting The Trade Desk’s value proposition could erode over time,” Wedbush analysts wrote on Friday.

The Wedbush analysts lowered their rating on The Trade Desk to the equivalent of hold from buy, and cited Amazon’s recent ad integration with Disney as a sign of the company’s aggressiveness.

Executives at The Trade Desk were asked about Amazon on the call, and responded by suggesting that the companies don’t really compete, emphasizing that Amazon is conflicted because it will always prioritize its own properties.

“A scaled independent DSP like The Trade Desk becomes essential as we help advertisers buy across everything and that we have to do that without conflict or compromise,” CEO Jeff Green said on the call. “It is my understanding that Amazon nearly doubled the supply of Prime Video inventory in the recent months. That creates a number of conflicts.”

For the second quarter, The Trade Desk reported a 19% increase in year-over-year revenue to $694 million, topping the $685 million estimate, according to analysts polled by LSEG. Adjusted earnings per share of 41 cents beat estimates by a penny.

Looking to the third quarter, the Trump administration’s tariffs were also a theme, as the company forecast revenue of at least $717 million, representing growth of 14% at minimum.

“From a macro standpoint, some of the world’s largest brands are absolutely facing pressure and some amount of uncertainty,” Green said. “Some have to respond more than others to tariffs. Many are managing inflation worries and the related pricing that comes with that.”  

With Friday’s slump, The Trade Desk shares are now down 53% for the year, while the S&P 500 is up about 9%. The Trade Desk was added to the S&P 500 in June.

WATCH: Trade Desk shares sink