Q:

A simple thermodynamic question?

I tried this question a lot of time and few day's earlier I also solved it correctly but I don't know why I am not able to solve it now. I can't get what link I am missing.
ques: 2 moles of helium gas undergo a cyclic process as shown. Assuming the gas to be ideal calculate the net change in heat energy, the net work done, the net change in internal energy
 
If any one would just be able to give me the basics to approach the ques this will also help me?

A:

I am not doing any of your calculations.  But consider A to B.  Since you know the temp change you know the energy change.  Since this is a isobaric process, the volume is increasing.  Therefore you can calculate the work done that the helium does on its environment.  Since you know energy change and work done you can calculate the heat exchange.  
For B to C the process is isothermal.  Since there is no energy exchange you know that the work done is equal and opposite to the heat exchange.  Since
$$W = \int p dV $$
and 
$$p = \frac{C}{V} $$
where C depends on your units (Boltzmann constant or ideal gas constant).  You can use this to integrate from V1 to V2 and solve for the work done.  
You dont need any more information than this for the last two processes.

