Can you please answer both parts of a and then part b, rounding to the nearest integer for part a and b

The 2010 census in a particular area gives us an age distribution that is approximately given (in millions) by the function f(x) = 39.9+ 2.1x - 0.867x where x varies from 0 to 9 decades. The population of a given age group can be found by integrating this function over the interval for that age group. (a) Find the integral over the interval [0,9]. (Round to the nearest integer as needed.) What does this integral represent? O A. The number of people in this area increased by about 233 million people aged 0 to 90 in 2010. O B. About 233 million people aged 0 to 90 have ever lived in this area from year 0 through 2010 O C. The total number of people in this area under 9 years old was about 233 in 2010. D. The total number of people in this area aged 0 to 90 was about 233 million in 2010. (b) Find the number of people alive in 2010 that were born in the fifties, that is, those in the range of 4 to 5 decades in 2010