A heat engine has a perfectly reversible "core" and the only imperfections are the mechanical friction and the two external heat conductors connecting it to the reservoirs which are at 400 K and 300 K. The hot conductor has a drop of 11 K, the cold one has a drop of 7 K. The mechanical losses are 50W and this energy is transferred to the cold reservoir. Calculate:
a) The efficiency of the "core" when operating as an engine
b) The performance of the "core" when operating as a heat pump