[填空题]
(a) A particular househ zzqklu+*;)d1 lsa 7y0bgs2 awold uses a 1.8-kbp9ueo(/iqiz8 t1 xt w8rz.l jy/h49 /zwh8gaW 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)? dollars per month
(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? kg of coal
