Read my section on Velocity and Acceleration starting on page 149. Look at my Lesson 5, question 5 and Practise Problems 86 and 87.
Part (a)
v is simply the derivative of
h(t); v = H'(t).
Part (b)
The ball stops rising when its velocity is 0. Find t where v=0. Just leave the answer as a mess. You can't be expected to get an exact answer without a calculator and calculators aren't allowed on the exam. You can use a calculator to give a neater, rounded off answer, but state the perfect answer, too.
Part (c)
The ball hits the ground when
H=0. Find t when H=0. If you do it correctly, there will be two answers for t, but one of those answers will clearly be inappropriate. That is because the ball is on the ground twice, once at the start, and once at the end.