Physics help with a pendulum problem?

A 0.43 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 the figure: a href="http://session.masteringphysics.com/problemet/1122041/1/Walker.8.14.jpg" rel="nofollow"http://session.masteringphysics.com/prob…/a