how wide is a bit on a 500 Mbps link?

hello,

i got a question and looking for answer.

question is

How wide is a bit on a 500 Mbps link?. What would its phyical length be on copper wire where propagation velcity is same as speed of light.

i got answer for 1st part as 2nsec but i am stuc in 2nd part.

can anybody help to answer my question?