There is a population of one horned horses in Pangea, and the original
population is 1000 individuals. If their birth rate is 10/1000 and their
death rate is 50/1000, there is an immgration rate of 10 per year from
Islandea, and an emigration rate of 20 per year to Mystique Island.
How long until the populaiton goes extinct? years
(Hint - divide the original population by the rate of change)