Edward C. answered 06/19/20
Caltech Grad for math tutoring: Algebra through Calculus
Ayana,
You can use properties of the first derivative to find when the function is a maximum. Just find the critical points where Q'(t) is equal to 0 or undefined, and then determine if the point is a maximum by checking to see if Q'(t) changes from positive to negative at the point.
For part b, just plug in the time you found in part a into the equation for Q.