The Radius of Curvature Of $y = x ^ { 3 } - 2 x$

Multiple Choice

The radius of curvature of $y = x ^ { 3 } - 2 x$ at (2, 4) is

A) 1
B) $\frac { 1 } { 2 \sqrt { 2 } }$
C) $\frac { 2 } { 5 \sqrt { 5 } }$
D) $\frac { 101 \sqrt { 101 } } { 12 }$
E) $\frac { 7 } { 125 }$