Gcse math

A pop concert has a crowd of 2000 people rounded to 1 significant figure.
A rock concert has a crowd of 2000 people rounded to 2 significant figures.

Work out the largest possible difference between the exact numbers of the two crowds.

For the two crowds, what's are their largest and smallest values, before the rounding?
Then which combination gives the largest difference?

I can not figure out what's their values before rounding.

Can you round to 1sig fig or 2 sig fig? For example, what do the following round to
1865, 1456, 2258, 2650
What are the critical values that make it round to one value rather than another?

If I round them to 1 s.f
2000,1000,2000,3000

So what are the min and max values that round to 2000 for 1 sig fig?