The question asks us to advise the company on a heat pump (and give reasons) which is claimed to deliver 1500J to a room at 280K by consuming 50J of work per cycle pumping heat from the surroundings at 270K.
I've drawn a diagram of the heat pump, taking heat Q2 from a bath of 270K up to an engine/refrigerator into which goes work W=50J, from which heat Q1 goes into hot bath of 280K. I am a bit confused about what to do next.
Is it that the efficiency of a heat pump is = Q1/W = Q1/ (Q1-Q2) = ????