Answer:
Answer: B. $0.78.
Explanation:
Cost of Electricity
The rate of the cost of electricity is usually expressed in $/kWh or cents/kWh because the consumption of electricity is measured in Kilowatts-hour.
The local power company charges 5.79 cents/kWh.
We are required to calculate the cost to run a 120 W stereo system for 4 hours per day for 4 weeks.
The total consumption time is 4 hours/day * 7 days/week *4 weeks = 112 hours
The total energy consumed is 120 W * 112 h =13,440 Wh.
Converting to kWh: 13,440 Wh/1,000 = 13.440 kWh.
Finally, we multiply by the cost rate: 5.79 cents/kWh * 13.440 kWh = 77.8 cents/100 = $0.78.
Answer: B. $0.78.
