What is the radius of convergence of the series $\sum _ { n = 0 } ^ { \infty } \frac { ( x - 4 ) ^ { 2 n } } { 3 ^ { n } }$ ? (A) $2 \sqrt { 3 }$ (B) 3 (C) $\sqrt { 3 }$ (D) $\frac { \sqrt { 3 } } { 2 }$ (E) 0