AP Work & Energy homework help!!?

A 0.30 kg pendulum bob is attached to a string 1.2 m long. What is the change in the gravitational potential energy of the system as the bob swings from point A to point B in Figure 8-22, where θ = 39°?
here is the image:
http://www.webassign.net/walker/08-19alt.gif
2 answers 2