A sample of Uranium is a mixture of two isotopes `._(92)^(234)U` and `._(92)^(238)U` present in the ratio `10%` and `90%` by weight. The half lives of these isotopes are `2.5 xx10^(5)` years and `4.5 xx10^(5)` years respectively. Calculate the contribution to activity in percentage of each isotope in this sample.