Answer:
A= 6
B = 99
C = 63
Explanation:

A) Getting the maximum we would need the derivative equal to zero.
The derivative is -
= 0 This means that the maximum is at t= 6. So it means it would take 6 hours.
B) The maximum score is done by placing the t= 6 into the formula and solving for s, which is the score. This will give us 99, the highest possible score.
C) if the student does no homework, it means he didn't spend any time on it and that means that t= 0.

As for the root question, plug it in the formula it should add up to zero, haven't done roots in a long time.
Hope this helps.