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 II.r'of water remaining in the tank [in gallons) after t minutes. t(min) 5 1o 15 20 25 30 v(gal) 690 445 255 112 29 o (a) IFP is the point {15, 255} on the graph of V, nd the slopes of the secant iines PQ when G is the point on the graph with t = 5, 10, 20, 25, and 30. {Round your answers to one decimai place.) Q slow (5: 690) E (10, 445} |:| (20, 112) |:| (25. 29) |:| (30- 0) E (b) Estimate the slope of the tangent iine at P by averaging the slopes of the two adjacent secant lines corresponding to the two points closest to P. (Round your answer to one decimal place.) :I