Answer:
The average rate of change in the balance over the interval t = 0 to t = 5 is of $20.82 a year. This means that the balance increased by $20.82 a year over the interval t = 0 to t = 5.
Step-by-step explanation:
Given a function y, the average rate of change S of y=f(x) in an interval
will be given by the following equation:

In this problem, we have that:

Find the average rate of change in the balance over the interval t = 0 to t = 5.


Then

The average rate of change in the balance over the interval t = 0 to t = 5 is of $20.82 a year. This means that the balance increased by $20.82 a year over the interval t = 0 to t = 5.
Is the same as the one you just did.
keep in mind that, going against the current, the current's speed erodes speed from your regular speed, whilst if you're going with the current, the current's speed adds to it.
now, in this case, you row 5mph, going upstream you're only doing 3mph, whatever happened to the other 2mph? well, the current speed eroded them, meaning the speed of the river is 2mph.
now, going downstream with the current, your regular speed is 5mph, and the current is 2mph, since the current adds to yours, then you're going 5 + 2, mph.