(a) A particular household uses a 1.8-kW heater 3.0 h/day (“on” time), four 100-W lightbulbs 6.0 h/day, a 3.0-kW electric stove element for a total of 1.4 h/day, and miscellaneous power amounting to 2.0 kWh/day if electricity costs $0.105 per kWh, what will be their monthly bill (30 d)?
(b) How much coal (which produces 7000 kcal/kg) must be burned by a 35%-efficient power plant to provide the yearly needs of this household?