Determine whether the series

${\displaystyle \underset{n=0}{\overset{}{}}}2(cosn)(\frac{1}{4}{)}^n$

s convergent or divergent, and if convergent, ind its sum.

convergent with sum $\frac{8}{3}$

convergent with sum $\frac{8}{5}$

convergent with sum $-\frac{5}{8}$

convergent with sum $-\frac{8}{3}$

divergent

convergent with sum $-\frac{8}{5}$