A student determined to test the law of gravity for he walks off a skyscraper stopwatch in hand, and starts his free fal

[answerhappygod]

A student determined to test the law of gravity for he walks off
a skyscraper stopwatch in hand, and starts his free fall (zero
initial velocity). Five seconds later, superman arrives at the
scene and dives off the roof to save the student. What must be the
height of the skyscraper sot that even Superman can’t save him?
(Assume that Superman’s acceleration is that of any freely falling
body)