[填空题]
A stone is dropped from the roofr8wlok, yj au(hv0-z8f h)t p4 of a rm xez *zhhg/s24 sf41building; 2.20 s after that, a second stone is thrown straigh fhex 4*zhms1 s42g/rzt down with an initial 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? $m/s$