Physics Simple Harmonic Motion question.?

A 505g mass oscillates with an amplitude of 12.0cm on a spring whose spring constant is 20.0N/m .

Determine the total energy.

My professor decided to completely skip energy I guess so I have no idea how to do this.

Steve2015-01-28T11:29:07Z

Etot = k*A²/2 = 20*(0.12)²/2 = 0.144 J