I believe it’s 80 hope it helps
Thinking about the graph of f(x), the rate of change is zero whenever there is an extremum.
First, differentiate f(x)

Next, find the zeros of f'(x) by factoring.

Now, we substitute these x-values into the
original equation to find the coordinates.
(-2.667, 11.481), (0, 2)
If I read correctly, 2456 pennies needs to be divided simply by 3 then rounded to the nearest hundredth. So you would do 2456/3 3 goes into 24 how many times? Then 3 goes into 5 how many times, then continue the pattern. Once you've gotten a decimal to the thousandth, round the number to the hundredth and there you go