A tank holds 1000 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 min 5 10 15 20 25 30 V gal 682 443 260 104 26 0 a If P is the point 15 260 on the graph of V find the slopes of the secant lines PQ when Q is the point on the graph with the following values Round your answers to one decimal place slope Q 5 682 10 443 20 104 25 26 30 0 b Estimate the slope of the tangent line at P by averaging the slopes of two adjacent secant lines Round your answer to one decimal place