The question reads

The ball is tossed up in the air from a tower 50m above the ground. If the ball has an inital velocity of 30m/s, how long will it take to hit the ground if a = -9.8m/s^2.

Now ive got my velocity function v = -10t +30, my height function h = -5t^2 +30t + 50, how can I find the total time?

Thank You!