Consider a country in which prior to industrialization the per capita birth and death rates are each 1.25 %/y.

 1. Consider a country in which prior to industrialization the per capita birth and death rates are each 1.25 %/y. At some point in time the population is exposed to a high level of air pollution, birth rates are unchanged, and after 100 years of living with higher air pollution, the population has shrunk by 20%. 

a. What was the residence time of the population prior to industrialization?

b. What is the death rate following the rise in the air pollution level, assuming it has some constant value tor those 100 years?