PV graph question (trying to determine the work)

[adam878787878]

Homework Statement

Look at the PV diagram of a system above. (attached) The units for P and V are atmospheric pressure atm and liter L. Process A to B and B to C are straight lines on it.
How much is the work done by the system from A to C in J?

Homework Equations

i know that work is the area under the graph, but when i add up areas, answer is wrong for some reason??

The Attempt at a Solution

W = .5(4*3) + .5(4*1.5) * 152J
= 1596J

this is wrong though
?

 

[physixguru]

>>>>Work Done is...[ p*delta V] i.e. pressure multiplied by CHANGE IN VOLUME.

This is enough for a hint...^^^