 Amazon.com Inc. AMZN, -6.72 disclosed overnight that it boosted its stake in electric-vehicle maker Rivian Automotive Inc. RIVN, -4.12 to more than 18 and initiated a stake in self-driving software company Aurora Innovation Inc. AUR, -2.64 of more than 5. Amazon said late Wednesday it now owns 162,086,884 shares of Rivian, or 18.1 of the shares outstanding, which at current prices would be valued at about 9.75 billion at current stock prices. 