[填空题]
A stone is dropped from the roof of a building; 2.20 s after that, afd81 d)y;qdq s sec:n w3xhk ei95gkq9rw ;ond stone is thrown straight down with an ;nr3 :ige9k9q w kw5hxinitial speed of $25 \; m/s$ and the two stones land at the same time. (a) How long did it take the first stone to reach the ground? $s$ (b) How high is the building? $m$ (c) What is the speed of the first stone just before it hit the ground? $m/s$ (d) What is the speed of the second stone just before it hit the ground? $m/s$