10g mixture of  $K_{2}C{r}_2{O}_7$ and $KMn{O}_4$ was treated with excess of KI in acidic medium, iodine liberated required  $100c{m}^3$ of  $2.2N$ sodium thiosulphate solution for titration. If the mass percent of $KMn{O}_4$ in the mixture Z, then what is the value of 2Z/5? Molecular mass of $KMn{O}_4=158gm/mol$ ; Molecular mass of $K_{2}C{r}_2{O}_7=294gm/mol$