Physics Help?

Helium in a toy balloon does work on its surrondings as it expands with a constant pressure of 2.52 x 10^5 Pa in excess of atmospheric pressure. The balloon's initial volume is 1.1 x 10^-4 m�, and its final volume is 1.50 x 10^-3 m�. Determine the amount of work done by the gas in the balloon.