Answer: Qc * (1 - Th/Tc)
Explanation: Â
Maximum Work done = Qh * η
                Wmax  = Qh * (1 - Tc/Th)
For reversible cycle of engine: Qc/Tc + Qh/Th = 0
                          Qh = -(Qc*Th)/Tc
Substituting Qh back into equation for work:
Wmax = -(Qc*Th)/Tc * Â (1 - Tc/Th)
Wmax = -(Qc*Th)/Tc + Qc
Wmax = Qc * (1 - Th/Tc)