Match the following (P) Gypsum salt (1) {\KAI} ( {\SO}_4) _2 \cdot 12 {\H}_2 {\O} (Q) Epson salt (2) {\FeSO}_4 \cdot 7 {\H}_2 {\O} (R) Alum (3) {\CaSO}_4 \cdot 2 {\H}_2 {\O} (S) Green vitriol (4) {\MgSO}_4 \cdot 7 {\H}_2 {\O}

Correct Answer is : P-3, Q-4, R-1, S-2