No friction at all anywhere. Let me explain the diagram in steps and the Q.
green colour let us start with. It represent a wedge on which there is mass of 10kg (red colour). That’s it the first picture.
dotted line in white represent when the block touches the bottom of the wedge.
represent the dotted yellow line which represents the direction of acceleration for 10 kg mass. Which is kind of like unknown or not in a symmetry.
Where the Q lies
The Dark yellow line represent displacements. Below one is AC I.e displacement of the wedge. Now , only thing in this Q what I don’t understand is that why is Displacement of mass 10kg BC even though the direction of acc for 10 kg is the dotted line.
If you wish to know why the dotted line , there is an example in my textbook which tells us that. Also , tells us that because of the dotted line kind of acceleration, we use pseudo force for solving such questions.