An air-cooled condenser is used to condense isobutane in a binary geothermal power plant. The isobutane is condensed at 85°C by air (c_p = 1.0 kJ/kg · K) that enters at 22°C at a rate of 18 kg/s. The overall heat transfer coefficient and the surface area for this heat exchanger are 2.4 kW/m² · K and 1.25 m², respectively. The outlet temperature of air is
(a) 45.4°C

(b) 40.9°C

(c) 37.5°C

(d) 34.2°C

(e) 31.7°C