Twelve dietary iron tablets were analyzed by the gravimetric procedure in Section 1-4 and the final mass

Question:

Twelve dietary iron tablets were analyzed by the gravimetric procedure in Section 1-4 and the final mass of Fe2O3 (FM 159.688) was 0.2774 0.0018 g. Find the average mass of Fe per tablet.(Relative uncertainties in atomic masses are small compared with relative uncertainty in the mass of Fe2O3. Neglect uncertainties in atomic masses in this problem.