Answer:
a) T(r) = r.D(r)
b) 975 people per square mile.
Step-by-step explanation:
(a)
The units of D(r) are
when multiplying the density by the area we get the amount of people in that area, so
(b)
The average rate of change of T(r) over the interval [5,7] is
but D(7) = 350 and D(5) = 100, so
and the average rate of change of T(r) over the interval [5,7] is 975 people per square mile.