Determine the Period and Amplitude Of $y = 3 \cos \left( \frac { x } { 7 } + \frac { \pi } { 4 } \right)$

Multiple Choice

Determine the period and amplitude of $y = 3 \cos \left( \frac { x } { 7 } + \frac { \pi } { 4 } \right)$

A) period: $\frac { 2 \pi } { 7 } ;$ amplitude: 3
B) period: $- \frac { 2 \pi } { 7 } ;$ amplitude: $- 3$
C) period: $\frac { \pi } { 7 }$ ; amplitude: 3
D) period: $7 \pi$ ; amplitude: 6
E) period: $14 \pi$ ; amplitude: 3