The path of a toy rocket is given by P (t) = -(t-3) + 21, where t is in seconds, and P is in meters.

The path of a toy rocket is given by P (t) = -(t-3)² + 21, where t is in seconds, and P is in meters. When is the maximum height reached by the rocket?(A) -3 secondsB) 2 secondsc) 0 secondsD) 3 seconds