On January 21, 2020, Mason exercised an incentive stock option (ISO) granted to him by his employer. His option enabled him to purchase 1,000 shares of stock for $15 per share. When he exercised his option, the stock was trading at $20 per share. He sold the stock at a gain six months later, when the stock was trading at $25 per share. As a result of this transaction, how much does Mason report on his 2020 return as short-term capital gain income?

$0

$5,000

$10,000

$15,000