A companys financial year runs from January to December. The following is a series of events concerning the companys stock:

1 January the company had 10,000,000 shares outstanding

1 April the company issued a 10% stock dividend

31 August 2,400,000 new shares were issued

1 December 30% of the shares in existence at this time were bought back

Estimate the number of shares that should be used to calculate basic earnings per share.