Determine the Amplitude or Period as Requested $y = \frac { 5 } { 8 } \cos \left( - \frac { 8 \pi } { 7 } x \right)$

Multiple Choice

Determine the amplitude or period as requested.
Graph Variations of y = cos x
-Period of $y = \frac { 5 } { 8 } \cos \left( - \frac { 8 \pi } { 7 } x \right)$

A) $\frac { 7 } { 4 }$
B) $\frac { 16 \pi } { 7 }$
C) $\frac { 5 \pi } { 4 }$
D) $\frac { 4 } { 5 }$