A cylindrical parabolic solar collector is designed to heat a fluid that enters the absorber at 140°C at a flow rate of 5 kg/min. The specific heat capacity of the fluid is 1.5 kJ/kg °C and its outlet temperature is 180°C. If the incident beam radiation on the plane of aperture is 3000 kJ/h m² and useful projected area of the reflector is 2 m × 10 m, the efficiency of the collector in percentage will be