Determine the Period and Amplitude of the Following Function $$y = 4 \cos \left( \frac { 3 x } { 4 } + \frac { \pi } { 4 } \right)$$

Multiple Choice

Determine the period and amplitude of the following function.
$$y = 4 \cos \left( \frac { 3 x } { 4 } + \frac { \pi } { 4 } \right)$$

A) period: $2 \pi$ , amplitude : 2
B) period: $10 \pi$ , amplitude : 2
C) period: $5 \pi$ , amplitude : 4
D) period: $\frac { 8 \pi } { 3 } ;$ amplitude : 4
E) period: $3 \pi$ , amplitude : 4