An impure sample of sodium oxalate $\left(N{a}_2{C}_2{O}_4\right)$. Weighing 0.20 g is dissolved in aq. Solution of $H_{2}S{O}_4$  and solution is titrated at  ${70}^{0}C$ required 45 ml of 0.02M $KMn{O}_4$ solution. The end points is over run, and back titration is carried out with 10 ml of 0.1M oxalic acid solution. Find % purity of $N{a}_2{C}_2{O}_4$ in the sample.
(round off to nearest integer)