Answer:
100 residents/

Explanation:
In order to find the population density, we have to calculate the area of the township first.
We know that:
L = length = 5 km
W = width = 4 km
So the area of the township is

Now we can find the population density by using

where N is the number of residents, and A is the area.
Substituting N = 2000, we find:

so, 100 residents per kilometer squared.