how to caluclate work ?

consider a 5.5 liter of a gas of 3.0 atm in a cylinder with a movable piston. The external pressure is changed so that the volume is changed to 10.5 Liter.

A. calculate the amount of work done

B. use the preceding data but consider the process to occur in two steps. At the end of the first, the volume is 7.0Liter. The second step results in a final volume of 10.5L. Calculate the work done and indicate the correct sign?

I dont get this at all please walk me though it