A powder contains FeSO4·7H2O (molar mass = 278.01 g/mol) among other components. A 3.075-g sample of the powder was dissolved in HNO3 and heated to convert all iron to Fe3 . The addition of NH3 precipitated Fe2O3·xH2O which was subsequently ignited to produce 0.304 g of Fe2O3. What was the mass of FeSO4·7H2O in the 3.075-g sample?