Find the Radius of Convergence and the Interval of Convergence $$\sum _ { n = 0 } ^ { \infty } \left( \frac { n x } { 6 } \right) ^ { n }$$

Multiple Choice

Find the radius of convergence and the interval of convergence of the power series.
$$\sum _ { n = 0 } ^ { \infty } \left( \frac { n x } { 6 } \right) ^ { n }$$

A) $R = 0 , I = \{ 0 \}$
B) $R = \infty , I = ( - \infty , \infty )$
C) $R = 6 , I = [ - 6,6 ]$
D) $R = 6 , I = ( - 6,6 )$