When a desktop personal computer is operating, its power supply is able to convert only about 65% of the supplied electrical power into the directcurrent electricity that the computer’s internal electronic components require.

The remainder of the energy is mostly lost as heat. On average, each of the estimated 233 million personal computers in the United States consumes 300 kW ∙ h of energy each year.

(a) If the efficiency of the power supply could be increased to 80% by using a new type of power supply that is under development (a so called resonance-based switching-mode system), how much energy could be saved each year? Express your answer in the conventional units of kW ∙ h for electricity.

(b) The United States produced 19.2 trillion kW ∙ h of electrical energy in 2007. By what percentage would the nation’s electricity needs decrease?

(c) At the cost of 12¢ per kW ∙ h, what would the cost savings be?