How many gram of pure $KMn{O}_4$ should be heated with $H_{2}S{O}_4$  to produce 48 gram $O_2$?
$$\begin{gathered} KMn{O}_4+H_{2}S{O}_4\to K_{2}S{O}_4+MnS{O}_4+H_{2}O+O_2 \\ [Mn=55,K=39,O=16,H=1,S=32] \end{gathered}$$