I'm pretty sure part a is right but I don't know how to do part b

Sec2.3: Problem 22 Previous Problem Problem List Next Problem (1 point) Book Problem 43 If a ball is thrown vertically upward from the roof of 64 foot building with a velocity of 80 fu/sec, its height after t seconds is s(t) - 64 + 80t - 16t2. a) What is the maximum height the ball reaches? 164 b) What is the velocity of the ball when it hits the ground (height 0)? I Hint: Note: You can earn partial credit on this problem. Preview My Answers Submit Answers