Hi,
Can you help me figuring this exercise on thermodynamics?

"A cylinder with a movable piston contains a certain quantity of helium. With a very slow transformation - represented in a V-p graph as a straight line - it goes from state to state . It is then subjected to a costant-volume transformation followed by a costant-pressure one, returning to the initial state".

I had a graph but couldn't post it. Anyway, from there it was pretty simple to find the work done (area of the triangle of the three states): .
It was a counterclock-wise transformation, hence the negative work.

It then asks for , which I calculated from the ideal gas law. I didn't know the amount of substance, but I took that from state A. then .

Finally, it wants the heat transfer with the outside during .
At first, I wanted to use , but the specific heat gave me some doubts: which one should I use when the transformation is not particular (I'm referring to the fact that there are specifc specific heats when the transformation is with costant pressure/costant volume)?
Then I thought I could use . I could calculate the difference in internal energy: .

Since it is work done on the gas, it is more internal energy, not less: . Also, we are only talking about the work done from A to B, which includes the area underlying the triangle: . But I can't figure out the sign of the Q: the work causes a compression, but I don't know how much. I mean: it could be so much that the temperature went much higher than 375K, arriving then at that level giving off heat; but it could also be that the work brought the temperature under 375K and that it arrived at that level absorbing heat.
And anyway, whatever sign I use the answer , the book says) isn't right. And I'm stuck here.

Where is my mistake?
Thanks in advance!
(If something isn't clear, please tell me)