Tesla’s stock jumped more than 8% in New York trading on Monday after CEO Elon Musk disclosed that he purchased more than 2.5 million shares worth roughly $1 billion through a trust. The purchase marks his first open-market buy of Tesla stock in over five years. Tesla’s stock opened at $428.05 on the NASDAQ. The timing of Musk’s purchase is notable. To unlock the package, Musk must also drive Tesla’s market capitalization from its current level of around $1.3 trillion to an unprecedented $8.5 trillion.