The bar graph shows the population of the United States, in millions, for six selected yea...

The bar graph shows the population of the United States, in millions, for six selected years.

Source: U.S. Census Bureau

Here are two functions that model the data:

Use the functions to solve Exercises .

a. Write a function that models the total U.S. population for the years shown in the bar graph.

b. Use the function from part (a) to find the total U.S. population in 2005.

c. Does the result in part (b) overestimate or underestimate the actual total U.S. population in 2005 shown by the bar graph? By how much?