F is employed by a public corporation. In year 1, F was granted a stock option to acquire 3,000 shares from the treasury of her employer's corporation for $10 a share. At the time of receiving the option, the shares were valued at $12 per share. In year 4, F exercised her option and purchased 3,000 shares for $30,000. At the purchase date, the shares were valued at $13 per share. In year 6, F sold 3,000 shares for $18 per share. What amount is included in F'soverall net incomefor tax purposes in year 6?