The rate of fuel consumption, r(t), recorded during a portion of an airplane flight is increasing and differentiable. Use the graph of r(t) to answer the following questions. Consumption Rate (gallons/min) 180 160 (90,152) 140 (70,128) 120 100 (50,104) 80 60 (30,60) 40 20 Time (mini 10 20 30 40 50 60 70 80 9 (a) Estimate r(t) dt using a left-hand sum with At = 20 --units- (b) Which of the following could be a practical interpretation of (t) dt ? -Select- v (c) Which of the following quantities below would measure the average rate of fuel consumption during the first 50 minutes of the flight? O (50) - (0) 50 O 1 50 0 r(t ) dt 50 r( t ) at O r(50) - r(0)