Find the Amplitude of the Function $$y = 5 \cos \frac { 1 } { 4 } x$$

Multiple Choice

Find the amplitude of the function.
- $$y = 5 \cos \frac { 1 } { 4 } x$$

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