Find the Requested Function Value $( g \circ f ) ( 13 )$

Multiple Choice

Find the requested function value.
-Find $( g \circ f ) ( 13 )$ when $f ( x ) = \frac { x - 3 } { 2 }$ and $g ( x ) = 3 x + 1$

A) 200
B) 16
C) 20
D) $\frac { 37 } { 2 }$