1st law of thermodynamics, work/heat

[FlipStyle1308]

Homework Statement

http://img404.imageshack.us/img404/1913/captureop6.jpg

Homework Equations

adiabatic expansion: q = 0
deltaU = w = Cv (T2-T1)
reversible (ideal gas): P1V1 = P2V2
gamma = Cp/Cv
Cp - Cv = R

The Attempt at a Solution

V1 = nRT/P1
V2 = nRT/P2
Combine into w = -P2 (V2 - V1)

This is where I got stuck.

 

[buffordboy23]

Use the ideal gas law equation to find the temperatures first. Did you do this? What are the temperatures at states 1,2, and 3?