A 25-W compact fluorescent lightbulb (CFL) produces the light equivalent of a 100-W incandescent bulb. The population of North America is estimated to be about 305 million. Estimate the amount of coal needed to light one 100-W incandescent lightbulb for each person for one year and the amount of coal that would be saved if each incandescent bulb were replaced with a CFL. Assume the coal has a NHV of 28.5 MJ · kg−1 and the power plants are 33% efficient.

A2-m rigid tank initially contains saturated water vapor at 100 kpa. the tank is connected to a supply line through a valve. steam is flowing in the supply line at 600 kpa and 300 c. the valve is opened, and steam is allowed to enter the tank until the pressure in the tank reaches the line pressure, at which point the valve is closed. a thermometer placed in the tank indicates that the temperature at the final state is 200°c. determine (a) the mass of steam that has entered the tank (b) the amount of heat transfer.