An air refrigeration system of 5 tons cooling capacity is employed to maintain the temperature of a refrigerated space at \(-20^{\circ} \mathrm{C}(253 \mathrm{~K})\) when the temperature of the surroundings is \(30^{\circ} \mathrm{C}(303 \mathrm{~K})\). The pressure ratio of the compressor is 4 . The specific heat of air may be taken as \(1.008 \mathrm{~kJ} / \mathrm{kg}\) and \(\gamma=1.4\).

Estimate

(a) The coefficient of performance of the system

(b) The mass flow rate of air as working medium

(c) The work of compression

(d) The work of expansion

(e) The net work of the system.