The 2000 census in a particular area gives us an age distribution that is approximately given (in millions) by the function f(x) = 39.4 + 2.12x - 0.786x2 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]. D (Round to the nearest integer as needed.) What does this integral represent? '1'} A. The number of people in this area increased by about 249 million people aged 0 to 90 in 2000. B. The total number of people in this area under 9 years old was about 249 in 2000. if} C. About 249 million people aged 0 to 90 have ever lived in this area from year 0 through 2000. D . The total number of people in this area aged 0 to 90 was about 249 million in 2000. b. Find the number of people alive in 2000 that were born in the fifties, that is, those in the range of 4 to 5 decades in 2000. million (Round to the nearest integer as needed.)