If the same plant is used as a heat-pump system, then the COP of the heat pump becomes

Question

 A refrigeration plant is designed to work between –3⁰C and 27⁰C.  The plant work on the Carnot cycle.  If the same plant is used as a heat-pump system, then the COP of the heat pump becomes

                                          

(a) 10      (b) 9  (c) 8        (d) 7