MY NOTES PRACTICE P A tank holds 1,000 gallons of water, which drains from the bottom of the tank in half an hour. The values in the table show the volume V of water remaining in the tank (in gallons) after t minutes. t (min) 25 5 10 15 20 25 30 V (gal) 686 438 255 116 28 0 (a) If P is the point (15, 255) on the graph of V, find the slopes of the secant lines PQ when Q is the point on the graph with t-5, 10, 20, 25, and 30. (Round your answers to one decimal place.) Q Slope (5,686) (10, 438) (20,116) (25, 28) (30, 0) (b) Estimate the slope of the tangent line at P by averaging the slopes of the two adjacent secant lines corresponding to the two points dosest to P. (Round your answer to one decimal place.)