If the sum of an infinite GP a, ar, ar^2, ar^3, … is 15 and the sum of the squares of its each term is 150, then the sum of a r^2, a r^4, a r^6, … is:

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