Find the Given Trigonometric Function of the Indicated Angle Using $a = 8 , b = 18 , c = 25$

Find the given trigonometric function of the indicated angle using triangle ABC. cos C, where $a = 8 , b = 18 , c = 25$

A) $\frac { 2 } { 5 }$
B) $\frac { 8 } { 25 }$
C) $\frac { 18 } { 25 }$
D) $\frac { 25 } { 18 }$
E) $\frac { 8 } { 19 }$