Assignment:
An efficiency study conducted for the Cassiopeia cabbage Company showed that the number of cases of cabbage packed by the average worker t hours after starting work at 8a.m. is given by -t^3+4t^2+12t, 0 or greater than t or greater than 4.
At what time during the morning shift is the average worker at peak efficiency?
Provide complete and step by step solution for the question and show calculations and use formulas.