approximately 82.6 million Americans will be at least 65. The bar graph shows the estimated number of Americans with projected figures for the year 2020 and beyond. A graphing calculator screen displays an exponential function that models the U.S. population age 65 and over, y, in millions, x years after 1899. Use this information to solve (a) (d) below. Click the icon to view the bar graph. ExpReg y = a-b^x a = 3.363809536 b = 1.023357735 OB. An exponential function was used because population is always modeled using exponential functions. OC. An exponential function was used because there are too many data points to use a linear function. O D. An exponential function was used because exponential functions are always more accurate than linear functions. b. Use the graphing calculator screen to express the model in function notation, with numbers rounded to three decimal places. f(x)= 3.364 1.023 c. According to the model in part (b), how many Americans age 65 and over were there in 2010? Use a graphing calculator. million (Type an integer or a decimal rounded to one decimal place as needed.)