If the sum of an infinite GP \(\mathrm{a}, \mathrm{ar}, \mathrm{ar}^2, \mathrm{ar}^3, \ldots\) is 15 and the sum of the …

If the sum of an infinite GP \(\mathrm{a}, \mathrm{ar}, \mathrm{ar}^2, \mathrm{ar}^3, \ldots\) is 15 and the sum of the squares of its each term is 150 , then the sum of \(\operatorname{ar}^2,\operatorname{ar}^4, \operatorname{ar}^6, \ldots\) is :