HighTech Company has 1,500,000 common shares outstanding on January 1, 2010. During 2010, HighTech had the following common stock transactions:

300,000 common shares were sold on April 1.

A 5-for-4 stock split was declared and paid on June 1

200,000 common shares were sold on July 1.

A 200% stock dividend was declared and paid on December 1.

What number of shares of common stock should be used in computing diluted earnings per share for 2010?

a. 2,000,000

b. 7,500,000

c. 6,768,750

d. 4,512,500