tolong bantu diselesaikan beserta caranya

h(t) = 150t - 5t^2
a) v(t) = dh/dt = 150 - 10t
b) tinggi maksimum diperoleh jika v(t) = 0
150 - 10t = 0
150 = 10t
t = 15
h(15) = 150(15) - 5(15)^2 = 2250 - 1125 = 1125 m