Twenty dietary iron tablets with a total mass of 22.131 g were ground and mixed thoroughly. Then 2.998 g of the powder was dissolved in concentrated HNO3 and heated to convert all the iron to Fe3+. Addition of NH3 caused quantitative precipitation of Fe2O3 (FW 159.69). The mass of the precipitate is 0.765 g. What is the average mass of iron in each tablet?