Answer: The cost of using the microwave oven for 30 minutes every day for 9 days is $0.57
Explanation: The GRASS method is used to calculate the cost of using an appliance by multiplying the power rating of the appliance (in kW) by the hours of use, and then multiplying that by the rate per kWh.
Here's the calculation:
Power rating: 0.62 kW
Time of use: 30 minutes/day for 9 days = 30/60*9 = 13.5 hours
Cost per hour = 0.62 * 6.8 / 100 = 0.04236
Total cost = 0.04236 * 13.5 = $0.57