3. One lb of oxygen, O2, in a piston-cylinder assembly undergoes a cycle consisting of the following processes: Process 1-2: Constant-pressure expansion from T1 = 500R p1 = 30 lbf/in to T2 = 1120R. Process 2-3: Compression to T3 = 800R and p3 = 53.3 lbf/in with Q23=-60 Btu. Process 3-1: Constant-volume cooling to state 1. Employing the ideal gas model with cp evaluated at T1, determine the change in specific entropy, in Btu/lb R, for each process. Table A-20E contains specific heat data for ideal gases. Sketch the cycle on p -v and T- s coordinates.