When a system is taken from stare a to stare b in Fig. 19.28 along the path

Question:

When a system is taken from stare a to stare b in Fig. 19.28 along the path acb, 90.01 of heat flows into the system and 60.0 J of work is done by the system.
(a) How much heat flows into the system along path adb if the work done by the system is 15.0 J?
(b) When the system is returned from b to a along the curved path, the absolute value of the work done by the system is 35.0 J. Does the system absorb or liberate heat? How much heat? (c) If Ua = 0 and Ud = 8.0 J, find the heat absorbed in the processes ad and db.