2a. Assume that the world population is 7.5 billion people and that the birth rate is 2.25% and the death rate is 1.50%. How many years will it take in order for the population to reach 15 billion?

2b. A pathogen spreads at .5% per day in a population if unchecked. In how many days will the number of people in a population affected by the pathogen quadruple?