I-86. (*) The U.S. penny was originally minted entirely of copper. However, after the year 1857 the U.S. penny was made of a variety of metals because of the high cost of copper. Since 1982 pennies have been made of zinc plated with a thin layer of copper. The modern penny weighs 2.500 grams, has a diameter of 19.05 millimeters, and an average thickness of 1.224 millimeters. Given that the density of copper and zinc are 8.96gcm3 and 7.13gcm3, respectively, determine the percentage by mass of copper in a modern penny