Is the Straight Line in a Carnot Cycle Graph Isobaric or Isothermal?

[gema]

Homework Statement

Consider the gas do the themodynamics process. If the process graph is one line with constant gradient,

Homework Equations

What process was happened?
How to calculate its amount of heat which absorbed or liberated?

The Attempt at a Solution

I really need your help.
I really am confuse. Is that isotermal,or isobaric ?

 

[LoadedAnvils]

Remember the stages of the Carnot cycle. How does a straight line apply here?