CPM Homework Help : PC Problem 2-173

First quadrant curve, titled spawning rate of salmon, x axis labeled minutes, scaled in twenties from 0 to 60, y axis scaled in tens from 0 to 50, with the following approximate points: starts at (0, comma 22), turning down @ (20, comma 52), turning up @ (25, comma 30), turning down @ (40, comma 30), turning up at (50 comma 20), turning down at (55, comma 50), area below the curve is shaded. The graph to the right shows the rate of salmon entering a fish hatchery during a $60$ minute period.

A gate fell during the time interval disrupting the flow of the salmon. About what time did this occur?
Hint (a):
Where does the graph have a maximum followed by a steep decrease?
What does the shaded area represent?
Hint (b):
Multiply the units on the axes.