A Hyperloop pod competition would follow up on Musk's a high-speed transit concept.
The burger chain's shares were up more than 130 percent this morning.
Some suggest the electric car company's shares had risen for the wrong reasons.
Ballmer said he plans to devote much of his attention to the Los Angeles Clippers basketball team, which he recently bought for $2 billion.
The social-media company saw a 24 percent jump in monthly average users in the second quarter.
The online retail giant said it expects an operating loss of as much as $810 million for the current quarter, sharply below analysts' estimates.
The consumer tech giant beat on profit and missed on revenue in the third quarter.
A supplier to the fast-food chains in China has been accused of using expired meat and allowing unhygienic practices.
The Chinese ecommerce giant officially filed to list its shares in the U.S. in what could be one of the biggest initial public offerings ever.