An irreversible heat engine extracts het from a high temperature source at a rate of 100kW and rejects heat to a sink at a rate of 50kW. The entire work output of the heat engine is used to drive a reversible heat pump operating between a set of independent isothermal heat reservoirs at 17 0C and 750C. The rate (in kW) at which the heat pump delivers heat to its high temperature sink is
(a) 50 (b) 250
(c) 300 (d) 360