[填空题]
A stone is dropped from uubt dxdqgvr6pg;8j ).q 2b3ja)w3y* the roof b x (y9qneom9pf-/1vt9 o(6gnfo*rwf of a high building. A second stone is dropped 1.50 s later. How far apart are the stones whenw*-xten fp9qy16vo99o /ffo(g(r bmn the second one has reached a speed of 12.0 m/s ? m