Water leaks from a tank at the rate of r(t) gallons per hour. the rate decreased as time passed, and values of the rate at two-hour time intervals are shown in the table below. the total amount of water that leaked out is evaluated by a riemann sum. find the upper estimate (left end-points of each rectangle) for the total amount of water that leaked out by using five rectangles. give your answer with one decimal place. (10 points)

t | r(t)

0 | 12.0
2 | 10.6
4 | 8.8
6 | 8.0
8 | 6.0
10 | 4.8