Homework Help: Thermodynamics question >_<

1. The problem statement, all variables and given/known data
A cylinder contains 2 moles of an ideal monatomic gas that is initially at state A with a volume of 1.0 x 10^-2 m3 and a pressure of 4.0 x 10^5 Pa. The gas is brought isobarically to state B. where the volume is 2.0 x 10^-2 m3. The gas is then brought at constant volume to state C, where its temperature is the same as at state A. The gas is then brought isothermally back to state A.
a. Determine the pressure of the gas at state C.
b. State whether this device is a refrigerator or a heat engine. Justify your answer.

So heres my version of that,

n = 2mol
stateA
v = 1.0 x 10^-2m³
p = 4.0 x 10⁵ Pa
stateB
v = 2.0 x 10^-2 m³
p = 4.0 x 10⁵ Pa (Isobaric Process)
stateC
v = 2.0 x 10^-2 m3 (Isochoric Process)
t_c = t_a
w = 0 (isochoric)
p = ?
2. Relevant equations
p=F/A?
w=pdeltav?
3. The attempt at a solution
a)i know that the fact t_c = t_a has something to do with this, but when i consider this i would get deltau to = 0 due to the isothermal process right? and if deltau = 0 then q=w then t=p.02? but then how would i solve for p if i don't know t? >_< this is confusing...
b)i know that if i made a pv graph for this id have something like A---->B then C directly under B but because i dont know the answer to question a i dont know exactly where, also does that even have anything to do with it? im guessing that with less volume you have higher temperature and the opposite with lots of volume but then my teacher showed us that in carnot cycles its actually colder when theres less volume!!! i would have to say refrigerator just because at b; the only state where temperature changes it would increase becauseto maintain the same pressure at an increased volume you would have to have a higher temperature right?
1. The problem statement, all variables and given/known data



2. Relevant equations



3. The attempt at a solution

 

help plz? :(