Problem 1: In the population growth problem, if
b-d > 0, the population will double its present size at time T,

2P(0) = P(0)e^((b-d)T)

or

e^((b-d)T)=2

or

T = ln(2)/(b-d)

where T is called the doubling period. If the world currently has a
population of 4.5 billion people and its doubling period is 30 years
(i.e., T=30), graph the population of the world after 30, 50, 100
and 200 years from now on the same graph. Hint: Utilize equation
(7.3).

Just for fun (not for credit), the surface area of the earth is about
1,860,000 billion square feet, how much space would each person have after
1000 years?