According to the 2010 census, the U.S. population was 309 million with an estimated growth rate of 0.8%/yr.

a. Based on these figures, find the doubling time and project the population in 2050.

b. Suppose the actual growth rate is just 0.2 percentage point lower than 0.8%/yr (0.6%). What are the resulting doubling time and projected 2050 population? Repeat these calculations assuming the growth rate is 0.2 percentage point higher than 0.8%/yr.

c. Comment on the sensitivity of these projections to the growth rate.