3. Incentive Stock Option Plans. In May 2020, employee N exercised an ISO that entitled him to purchase 50 shares of Clay Corporation common stock for $120 a share. The stock was selling on the open market for $210 per share. N sold the 50 shares in 2023 for $390 per share. a. How much income must N recognize in 2020 upon exercise of the option? b. How much income must N recognize in 2023 upon sale of the Clay stock