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22. The power of sunlight reaching each square meter of the Earth's surface on a clear day in the tropics is close to 1 000 W. On a winter day in Manitoba. the power concentration of sunlight can be 100 W/mQ. Many human activities are described by a power per unit area on the order of 102 \\N/m2 or less. (a) Con- sider, for example, a family of four paying $66 to the electric company every 30 days for 600 kWh of energy carried by electrical transmission to their house, which has floor dimensions of 13.0 m by 9.50 m. Compute the power per unit area used by the family. (b) Con- sider a car 2.10 m wide and 4.90 m long traveling at 55.0 mi/ h using gasoline having \"heat of combustion" 44.0 MJ/kg with fuel economy 25.0 mi/gal. One gallon of gasoline has a mass of 2.54 kg. Find the power per unit area used by the car. (c) Explain why direct use of solar energy is not practical for running a conventional automobile. (d) What are some uses of solar energy that are more practical? 76. A plane electromagnetic wave varies sinusoidally at 90.0 MHz as it travels through vacuum along the posi- tive x direction. The peak value of the electric field is 2.00 mV/m, and it is directed along the positive y direc- tion. Find (a) the wavelength, (b) the period, and (c) the maximum value of the magnetic field. (d) Write expressions in SI units for the space and time varia- tions of the electric field and of the magnetic field.Include both numerical values and unit vectors to indicate directions. (e) Find the average power per unit area this wave carries through space. (f) Find the average energy density in the radiation (in joules per cubic meter). (g) What radiation pressure would this wave exert upon a perfectly reecting surface at nor- mal incidence