Assume the annual rate of change in the national debt of a country (in billions of dollars per year) can be modeled by the function D'(t) = 852.47 + 817.02t - 167.912 + 18.0413 where t is the number of years since 1995. By how much did the debt increase between 1996 and 2008? . . . .. The debt increased by $ billion. (Round to two decimal places as needed.)