The rate (in liters per minute) at which water drains from a tank is recorded at half-minute intervals. Use the average of the left- and right-endpoint approximations to estimate the total amount of water drained during the first 3 min.

 $t$ min 0 0.5 1 1.5 2 2.5 3 l/min 44 42 40 38 36 34 32