For the Pair of Functions, Find the Indicated Sum, Difference $$f ( x ) = \sqrt { 3 x + 5 } , g ( x ) = \sqrt { 9 x - 16 }$$

For the pair of functions, find the indicated sum, difference, product, or quotient.
- $$f ( x ) = \sqrt { 3 x + 5 } , g ( x ) = \sqrt { 9 x - 16 }$$
Find $( f g ) ( x )$ .

A) $( \sqrt { 3 x + 5 } ) ( \sqrt { 9 x - 16 } )$
B) $( 3 x + 5 ) ( 9 x - 16 )$
C) $( 3 x + 5 ) ( 3 x - 4 )$
D) $( 3 x - 4 ) ( \sqrt { 3 x + 5 } )$