I need help I asked this like 3 times and they keep giving me the wrong answer.

The graph shows a city's daily rate of use of electricity (in millions of kilowatts). Estimate the total daily usage of electricity by using rectangles whose height is given by the value of the function at the left side of each rectangle. Let the width of each rectangle be 2 hours. Millions of kilowatts Midnight 4 A.M. 8 A.M. Noon 4 PM. 8 P.M. Midnigh The estimate of the city's total daily usage of electricity for the given day is |million kilowatt-hours. (Round to the nearest whole number as needed.)