The thermal efficiency of a Carnot engine is 1 TL/TH. This is assumed that the Carnot engine is in thermal equilibrium with the source and the sink during the heat addition and heat rejection processes, respectively. Thus, there is no external irreversibility. However, in reality, a reasonable temperature difference exists between the two heat transfer media to have an acceptable heat transfer rate through a finite heat exchanger surface area, where h and A are the heat transfer coefficient and heat transfer surface area, respectively. ENG-7001A Excellence CW December 2023 Page 8 of 9 a) Devise a relation to show the maximum net power output of a Carnot engine is related to h, A, TL, and TH. b) The heating cost for that day if resistance heating is used instead of the heat pump, assuming 34 pence per kWh. c) Plot the minimum theoretical operating cost for each day (assume 24 h) of operation of the heat pump as a function of T (indoor air temperature) from 18 to 23 C. What does the plot suggest?