An absorption air-conditioning system is to remove heat from the conditioned space at 20°C at a rate of 150kJ/s while operating in an environment at 35°C. Heat is to be supplied from a geothermal source at 140°C. The minimum rate of heat supply is
(a) 86 kJ/s
(b) 21 kJ/s
(c) 30 kJ/s
(d) 61 kJ/s
(e) 150 kJ/s