On October 15, 2020, the board of directors of Ensor Materials Corporation approved a stock option plan for key executives. On January 1, 2021, 38 million stock options were granted, exercisable for 38 million shares of Ensor's $1 par common stock. The options are exercisable between January 1, 2024, and December 31, 2026, at 80% of the quoted market price on January 1, 2021, which was $10. The fair value of the 38 million options, estimated by an appropriate option pricing model, is $3 per option. Ensor chooses the option to recognize forfeitures only when they occur. Ten percent (2 million) of the options were forfeited when an executive resigned in 2019. All other options were exercised on July 12, 2022, when the stock's price jumped unexpectedly to S19 per share.

Required:
a. When is Ensor's stock option measurement date?
b. Determine the compensation expense for the stock option plan in 2018. (Ignore taxes.)
c. What is the effect of forfeiture of the stock options on Ensor's financial statements for 2019 and 2020?
d. Is this effect consistent with the general approach for accounting for changes in estimates? Explain.
e. How should Ensor account for the exercise of the options in 2022?