Green Corporation was organized on January 1, 2020, with authorized capital of 500,000 shares of $10 par value common stock. During 2020, Green issued 30,000 shares at $12 per share, purchased 3,000 shares of treasury stock at $13 per share, and sold 3,000 shares of treasury stock at $14 per share. What is the amount of additional paid-in capital at December 31, 2020?

a. $0

b. $3,000

c. $60,000

d. $63,000