Maria Throws Two Stones from the Top Edge of a Building

Multiple Choice

Maria throws two stones from the top edge of a building with a speed of 20 m/s.She throws one straight down and the other straight up.The first one hits the street in a time t₁.How much later is it before the second stone hits?

A) 5 s
B) 4 s
C) 3 s
D) Not enough information is given to work this problem.