Solar radiation is incident on a flat-plate collector at a rate of 750 W/m2. The glazing has a transmissivity of 0.86 and the absorptivity of absorber plate is 0.95. The heat loss coefficient of the collector is 3 W/m2·oC. The collector is at an average temperature of 45oC and the ambient air temperature is 23oC. Determine the efficiency of this collector.