A tank holds 3,000 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)	5	10	15	20	25	30
V (gal)	2,076	1,302	765	357	87	0

(a)

If P is the point (15, 765) 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, 2,076)
(10, 1,302)
(20, 357)
(25, 87)
(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 closest to P. (Round your answer to one decimal place.)