On October 15, 2017, the board of directors of Ensor Materials Corporation approved a stock option plan for key executives. On January 1, 2018, 21 million stock options were granted, exercisable for 21 million shares of Ensor's $1 par common stock. The options are exercisable between January 1, 2021, and December 31, 2023, at 90% of the quoted market price on January 1, 2018, which was $10. The fair value of the 21 million options, estimated by an appropriate option pricing model, is $4 per option. Ensor chooses the option to recognize forfeitures only when they occur. Ten percent (2.1 million) of the options were forfeited when an executive resigned in 2019. All other options were exercised on July 12, 2022, when the stocks price jumped unexpectedly to $20 per share. Required: 1. When is Ensors stock option measurement date? 2. Determine the compensation expense for the stock option plan in 2018. (Ignore taxes.) 3. & 5. Prepare the necessary journal entries.