A free falling object problem?

Question

A rock is thrown vertically upward with a speed of 12.0 from the roof of a building that is 70.0 above the ground. Assume free fall.
Part A
In how many seconds after being thrown does the rock strike the ground?



Part B
What is the speed of the rock just before it strikes the ground?

Answer 1

Maximum height
ymax = 70 + sqrt(v0^2/(2g))
Time to max height
t1 = v0/g
Time from max height to landing
t2 = sqrt(2ymax/g)
A. Total time t = t1 + t2
B. v = sqrt(2g*ymax)