Height at an instance of time is given by :
h(t) = -4( t - 2 )² + 5 .....1
Differentiating above equation with respect to t .

Now, for maximum ,
.
8( t - 2 ) = 0
t = 2
Putting value of t = 2 in given equation, we get :
h( 2 ) = -4( 2 - 2 )² + 5
h( 2 ) = 5 m
Therefore, maximum height rocket can reach is 5 m.