The Position of a 2 $x = A \cos ( \omega t - \delta )$

Multiple Choice

The position of a 2.0-kg mass connected to a spring whose constant is 15 N/m is given by $x = A \cos ( \omega t - \delta )$ , where A = 25 cm and $\delta$ = $\pi$ /2. The total mechanical energy of the mass at time t = 0.30 seconds is

A) 0 J.
B) 0.34 J.
C) 0.47 J.
D) 1.0 J.