According to a certain estimate, the depth n(t), in centimeters, of the water in a certain tank at t hours past 2: 00 in the morning is given by n(t)= -20(t - 5)^2 + 500 for 0 ≤ t ≤ 10. according to this estimate, at what time in the morning does the depth of the water in the tank reach its maximum? a) 5: 30 b) 7: 00 c) 7: 30 d) 8: 00 e) 9: 00