Which best describes vibration? the distance traveled per unit in time
the action of moving back and forth quickly and steadily
the distance between one compression and the compression next to it
the action of moving through a material or substance

At the beginning of 1974/75,2 years a man invested #2000 in a bank at 12.5% compound interest, if it degree #650 at the end of each two years to pay his son's school fees, after payment of interest to pay his son's school fees, how much did he have left at the beginning of the 1978/79 school year?