A stone is dropped into a river from a bridge

A stone is dropped into a river from a bridge 43.9 m above the water. Another stone is thrown vertically down 1.00 s after the first is dropped. The stones strike the water at the same time.
(a) What is the initial speed of the second stone?
(b) Plot velocity versus time on a graph for each stone, taking zero time as the instant the first stone is released.