Does anyone know the answer to this ? (how to work it out would be very very useful, thanks)

Given that the speed of an electrical signal in a piece of cable is
2 * 10 8 metres/sec, how long does it take for a signal to get from one end of a 750 metre Ethernet to the other?

1 ) 15 microsec
2 ) 37.5 microsec
3 ) 3.75 millisec
4 ) 1.5 microsec
5 ) 3.75 microsec