Engineering Mechanics Dynamics

A hollow block is accidentally dropped by a laborer working in a high rise building. four seconds after it strikes the ground, an explosion like sound was heard by the laborer. the velocity of sound is 320 minutes per seconds.

1. In what storey number of the building the laborer is located if the height per storey is
3 meters?
2. What is the time of the hollow block to reach the ground?
3. what is the time of sound to travel the distance equal to the position (height) of the
laborer?