During a thermodynamic process, a system goes from state A to state B. They supply 800 J of heat and the system does 200

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During a thermodynamic process, a system goes from state A to
state B. They supply 800 J of heat and the system does 200 J
of work.
(a) For this transition, what is the change in the internal energy
of the system?
(b) If the system then moves from state B to state A, what is its
change in internal energy?
(c) If work is done in moving from A to B along a different path,
=900 J over
the system, how much heat is exchanged? Was heat absorbed or
released? Justify your answer.