Find the Period and Amplitude of the Function $y = 3 \cos 2 x$

Multiple Choice

Find the period and amplitude of the function $y = 3 \cos 2 x$ .

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