Find the Specified Domain $( f g ) ( x )$

Multiple Choice

Find the specified domain.
-Find the domain of $( f g ) ( x )$ when $f ( x ) = \sqrt { 5 x + 4 }$ and $g ( x ) = \sqrt { 5 x - 6 }$

A) $[ 0 , \infty )$
B) $\left[ - \frac { 6 } { 5 } , \infty \right)$
C) $\left[ \frac { 6 } { 5 } , \infty \right)$
D) $( - \infty , \infty )$