Solve the Problem $s ( t ) = - 5 \cos 5 \pi t$

Multiple Choice

Solve the problem.
-The position of a weight attached to a spring is $s ( t ) = - 5 \cos 5 \pi t$ inches after $t$ seconds. When does the weight first reach its maximum height?

A) After $\frac { 5 } { 4 } \mathrm { sec }$
B) After $\frac { 1 } { 5 } \sec$
C) After $\frac { \pi } { 5 } \sec$
D) After -