\textbf{197.} If 0.15 mol of a cation from a divalent metal undergoes a complete reaction with phosphate anions and forms a compound with a mass of 13.1 grams, which metal does this cation belong to?\\
$(O = 16, Mg = 24, P = 31, Ca = 40, Fe = 56, Zn = 65 : \text{g.mol}^{-1})$
\begin{center}
Mg (4) \qquad Zn (3) \qquad Fe (2) \qquad Ca (1)
\end{center}