G is employed by a Canadian-controlled private corporation. In year 1, G was granted a stock option to acquire 3,000 shares from the treasury of his employers corporation for $10 a share. At the time of receiving the option, the shares were valued at $12 per share. In year 3, G exercised his option and purchased 3,000 shares for $30,000. At the purchase date in year 3, the shares were valued at $13 per share. In year 6, G sold 3,000 shares for $18 per share. What amount is included in Gs employment income for tax purposes in year 6?