Write a Function Defined by Y = F (X) Subject $f ( x )$

Write a function defined by y = f (x) subject to the following conditions.
-The value of $f ( x )$ is nine times the square root of $x$ .

A) $f ( x ) = 9 x ^ { 2 }$
B) $f ( x ) = \sqrt { 9 x }$
C) $f ( x ) = 9 \sqrt { x }$
D) $f ( x ) = ( 9 x ) ^ { 2 }$