One company had 40,000 common shares outstanding for all of 2020. Additionally, the company had 20,000 convertible preferred shares outstanding, issued in 2019. Each preferred share is convertible into two common shares. On August 1, 2020, 18,000 preferred shares were converted to common shares. Also, the company issued 30,000 options on July 1, 2020. The options allow you to buy 30,000 common shares at $ 25 per share. The average market price for the second half of 2020 was $ 30 per share. On October 1, 2020, 12,000 options were exercised.

Calculate the weighted average number of common shares outstanding for the purpose of 2020 basic earnings per share.