Marco, Inc. determined the following information concerning its common stock during 2020: January 1 15,600 shares outstanding March 1 Issued a 3-for-1 stock split July 1 Issued 1,500 additional shares October 1 Reacquired 2,000 shares Required: What should Marco, Inc. use as the denominator for its basic earnings per share calculation for 2020? Round intermediate and final answer to the whole number. Weighted average number of common shares outstanding fill in the blank 1