Hmm. Let me just give you a little more detailed answer to the problem.

First the question asks you for Temp. so find that using PV=nrT (you have all the values given for points 1,2,3 from the graph)

Then start by finding U for each processes (using deltaU = w = Cv (T2-T1)) (Also, this equation is still valid even if the process is not constant volume). For process 3==>1, since its isothermal U=0 since u is only dependant on T which doesn't change.

Next find work using w=-nrT(ln(V2/V1)) since all process are reversible and in process 2==>3 use this for work since p is changing w=-nrT(ln(p1/p2)

Next use the first law of thermodynamics u=w + q to find q for all process

Then for H use H=Cp(T2-T1) for the first process 1==>2 (again dosn't matter if pressure is constant or not although it is).For process 3 ==>1, H=0 since isothermal

Next to find the total cycle put all the answers you got into a table like this and just add up the values for the total cycle of each. Careful of the signs

Path q w u H

1-2

2-3

3-1

Cycle

Remember to use proper units for each of the equations and values

Good luck>> >