JEE Math Practice Question

Let the sum of an infinite G.P., whose first term is a and the common ratio is r, be 5 . Let the sum of its first five terms be $$\frac{98}{25}$$. Then the sum of the first 21 terms of an AP, whose first term is $$10\mathrm{a r}, \mathrm{n}^{\text {th }}$$ term is $$\mathrm{a}_{\mathrm{n}}$$ and the common difference is $$10 \mathrm{ar}^{2}$$, is equal to :

1. A.$$21 \,\mathrm{a}_{11}$$
2. B.$$22 \,\mathrm{a}_{11}$$
3. C.$$15 \,\mathrm{a}_{16}$$
4. D.$$14 \,\mathrm{a}_{16}$$