1-68. Today, the best commercially av panels are about 18% efficient at converting theola rcially availabl ergy from sunlight into electricity. A typical ho in the United States uses about 40 kw.h of e ity a day, and U.S. electricity costs currently averag about $0.10 per kW-h. (a) Assuming 8.0 hours of te ful sunlight per day with an incident solar energy of 0.5 kW.m2, calculate the minimum panel area needed to provide for a typical home's electrical needs. Wil a solar panel of this size fit on the roof of a typical single-family home? (b) If it costs $15000 to install a solar panel of this size, how long will it take to pay for itself? Assume U.S. energy prices remain constani ec over this time