what does the statement "band limited signal of 5 KHz" mean
The nature of the words in the question is slightly ambiguous.


A Band-limited signal of bandwidth 5Khz means that the signal can be centered at any frequency but its extent around that frequency is 5Khz.
A Band-limited signal of 5Khz is also used to represent a signal which is having a center frequency of 5Khz but which has a fixed band-width.
It surely does not mean -2.5 to 2.5 because when mentioning the band-width usually the positive frequencies alone are counted.


I would advice you to revisit the text and look with respect to the above points.