Give the Amplitude or Period as Requested $y = 5 \cos \frac { 1 } { 4 } x$

Multiple Choice

Give the amplitude or period as requested.
-Amplitude of $y = 5 \cos \frac { 1 } { 4 } x$

A) $8 \pi$
B) $\frac { \pi } { 5 }$
C) 5
D) $\frac { 5 \pi } { 4 }$