Indicate the largest relative molecular weight from the group of the listed

Indicate the largest relative molecular weight from the group of the listed oxides – potassium oxide, chromium (III) oxide, copper (II) oxide, sulfur (VI) oxide.

It is necessary to calculate the relative molecular weights of oxides using the periodic system of D.I.Mendeleev:
1) Mr (K2O) = Ar (K) * N (K) + Ar (O) * N (O) = 39 * 2 + 16 * 1 = 94;
2) Mr (Cr2O3) = Ar (Cr) * N (Cr) + Ar (O) * N (O) = 52 * 2 + 16 * 3 = 152;
3) Mr (CuO) = Ar (Cu) * N (Cu) + Ar (O) * N (O) = 64 * 1 + 16 * 1 = 80;
4) Mr (SO3) = Ar (S) * N (S) + Ar (O) * N (O) = 32 * 1 + 16 * 3 = 80.

Answer: Cr2O3 has the highest relative molecular weight, which is 152.