The radiant energy incident on the earth's surface on a sunny day is roughly 900 w/m2. collecting and focusing sunlight and using the focused beam to heat a fluid is an old idea, and as the environmental costs of fossil-fuel combustion mount, solar heating becomes an increasingly attractive alternative. suppose a house is to be designed that will have a circulating forced-air central-heating unit, and solar energy is contemplated as a heat source (backed up with a conventional furnace to be used on cloudy days). if air is to be fed at a rate of 1750 m3/min at 20°c and 1 atm, and the air is to be heated to 55°c before being discharged into the living space, what is the required area of the solar collector plates? assume 30% of the radiant energy incident on the plates is used to heat the air.