The graph shows a city's daily rate of use of electricity (in millions of kilowatts). Estimate the total daily usage of electricity by summing the area of rectangles. Use the left endpoints, then the right endpoints, then give the average of those results as the answer. Let the width of each rectangle be 2 hours. 14- 12 10 8 Millions of kilowatt-hours NA O O O N 6- 4 2 من Midnight 4 A.M. 8 A.M. Noon 4 P.M. 8 P.M. Midnight The estimate of the city's total daily usage of electricity for the given day, found by averaging the estimates using left and right endpoints, is million kw-hrs. (Round to the nearest whole number as needed.)