On June 1, 2017, the stockholders of Best Seal Company approve a plan that grants 100 million stock options to the company’s executives and rank-and-file employees to purchase 100 million shares of the company’s $1 par value common stock. The company grants 60 million options on January 1, 2018. All executives and employees have to work for the company for three years before they may exercise the options at any time within the next 10 years. The option’s exercise price per share is $50, and the market price of the shares at the date of grant is $50 per share. Under the fair value method, the company computes total compensation expense by applying an acceptable fair value option-pricing model. The fair value option-pricing model determines the unit cost of stock options is $25 (total compensation expense to be $1,500 million. The tax rates are 20% for all years. On November 1, 2021, 15 million stock options are exercised when the market price is $90.
How much is the ending balance of deferred tax regarding the stock options by the end of year 2020?