Phosphoric acid, a mild acid used among other things as a rust inhibitor, food additive, and etching agent for cavity repair by dentists, can be made from elemental phosphorus in a two step process. in the first step, phosphorus and oxygen react to form diphosphorus pentoxide: in the second step, diphosphorus pentoxide and water react to form phosphoric acid : suppose the yield of the first step is and the yield of the second step is . calculate the mass of phosphorus required to make of phosphoric acid. be sure your answer has a unit symbol, if needed, and is rounded to significant digits.