This is how i got the result, i hope it is correct!
The exact volume would be 80 feet long
The answer is 25% if you subtract 55 by 30 you will get 25
<u>ANSWER</u>
The zeros are 
EXPLANATION
Given;
.
We can rewrite the function as



The zeros are found by equating the function to zero.


The multiplicity is 1, since it is odd the graph crosses at this intercept. which is 
Or

The multiplicity is 1, since it is odd the graph crosses at this intercept. which is 
Or

This last root has a multiplicity of 2.
That is
repeats two times.
Since the multiplicity is even, the graph touches the x-axis at the point
.
See graph.