Pronghorn Inc. uses a calendar year for financial reporting. The company is authorized to issue 9,720,000 shares of $10 par common stock. At no time has Pronghorn issued any potentially dilutive securities. Listed below is a summary of Pronghorn's common stock activities. 2. Number of common shares issued and outstanding at December 31, 2018 Shares issued as a result of a 10% stock dividend on September 30, 2019 Shares issued for cash on March 31, 2020 Number of common shares issued and outstanding at December 31, 2020 A 2-for-1 stock split of Pronghorn's common stock took place on March 31, 2021 1,910,000 191,000 1,830,000 3,931,000 4. Compute the weighted average number of common shares used in computing earnings per common share for 2019 on the 2020 comparative income statement. shares Compute the weighted average number of common shares used in computing earnings per common share for 2020 on the 2020 comparative income statement. shares Compute the weighted average number of common shares to be used in computing earnings per common share for 2020 on the 2021 comparative income statement. shares Compute the weighted average number of common shares to be used in computing earnings per common share for 2021 on the 2021 comparative income statement. shares