red gold is a gold‑copper alloy used to make jewelry. a piece of jewelry made of red gold weighs 9.47 g9.47 g and has a volume of 0.715 cm30.715⁢ cm3 . gold has a density of 19.3 g/cm 319.3⁢ g/cm3 and copper has a density of 8.96 g/cm 38.96⁢ g/cm3 . calculate the percentage by mass of each metal in the jewelry. assume the total volume of the jewelry is the sum of the volumes of the two metals it contains.