Describe the Transformations Required to Obtain the Graph of the Function

Multiple Choice

Describe the transformations required to obtain the graph of the function f(x) from the graph of the function g(x) .
- $$f ( x ) = 3 \cos x ; g ( x ) = \cos x$$

A) Horizontal stretch by a factor of 3
B) Vertical stretch by a factor of 3
C) Vertical shrink by a factor of $\frac { 1 } { 3 }$
D) Horizontal shrink by a factor of $\frac { 1 } { 3 }$