Determine the Constant of Variation for the Stated Condition $y$ Varies Directly as the Cube Of

Multiple Choice

Determine the constant of variation for the stated condition.
-If $y$ varies directly as the cube of $x$ , and $y = 5$ when $x = 2$ , find $y$ when $x = 8$ .

A) 320
B) 20
C) $\frac { 5 } { 4 }$
D) $\frac { 5 } { 64 }$