4. A refrigeration unit operates in an inverted Carnot cycle. It receives from the surroundings (at 27C) 10,000 kcal per hour. If the temperature inside the unit must be kept at -50C, what is the power of the unit's engine (recall that power is P = W/t)? A Carnot engine is an idealized, reversible engine. In real life, it is found that you need to use an engine capable of producing 5.50 kW to run this unit. Express the efficiency of this engine as a percent of the efficiency of the Carnot engine (e.g. a possible answer would be "the engine has 65% the performance of a Carnot engine"). Note, for refrigerators, we use the coefficient of performance, c, which is a concept equivalent to the efficiency of the Carnot engine. It is given by the ratio of the heat extracted from the cold source, qc. and the work done on the system: c= [qc/w] =T/(TH-Tc). c can be significantly larger than 1.