The fоllоwing infоrmаtion hаs been obtаined from the Mastic Corporation: 550,000 shares of common stock were outstanding on January 1, 20X1. Bonds convertible into 50,000 shares of common stock were issued on July 1, 20X1; the bonds have been determined to be dilutive. 36,000 shares of common stock were issued on November 1, 20X1. 24,000 shares of common stock were purchased on December 1, 20X1. What is the weighted average number of shares to be used in the calculation of diluted earnings per share for 20X1?