Riverbed Inc. uses a calendar year for financial reporting. The company is authorized to issue 8,210,000 shares of $12 par common stock. At no time has Riverbed issued any potentially dilutive securities. Listed below is a summary of Riverbed's common stock activities. 1. Number of common shares issued and outstanding at December 31, 2015 2. Shares issued as a result of a 12% stock dividend on September 30, 2016 3. Shares issued for cash on March 31, 2017 1,890,000 226,800 2,100,000 4,216,800 Number of common shares issued and outstanding at December 31, 2017 4. A 2-for-1 stock split of Riverbed's common stock took place on March 31, 2018 Compute the weighted-average number of common shares used in computing earnings per common share for 2016 on the 2017 comparative income statement. shares Compute the weighted-average number of common shares used in computing earnings per common share for 2017 on the 2017 comparative income statement. shares Compute the weighted-average number of common shares to be used in computing earnings per common share for 2017 on the 2018 comparative income statement. shares Compute the weighted-average number of common shares to be used in computing earnings per common share for 2018 on the 2018 comparative income statement. shares