a rock is thrown straight upward with an initial velocity of 50 m/s from a point 100 m above the ground. If the acceleration of the rock at any time t is a= -10 m/ , what is the maximum height of the rock (in meters)?

here's my attempt:

a(t)= -10t

take anti-derivative

v(0)= -5(0)^2+c

50= c

then i dont know what to do from here