In a cyclic process, where you end with the same state you started with, the change $$U in the internal energy of the system is zero. Therefore, for the cyclic process a$$b$$c$$d$$a$,$U $0,$ whichresultsinQ$$W accordingtothefirstlawofthermodynamics$($Equation$9).$Theheat added to the system in a cyclic process can be separated into the heat absorbed from the hot bath and the heat absorbed from the cold bath as Q $$ QH $$ QC $.$ Note that QC is a negative quantity, as

heat is actually removed from the system by the cold bath.