For the years 2005 through 2009, the annual rate of change in the national credit market debt, in billions of dollars per year, could be modeled by the function: D′ (t) = -810.3t 2 + 17.30t + 3648, where t is the number of years since 2005. Find the national credit market debt in 2009, given that D(0) = 41, 267. Explain the process you used to find the national credit market debt in 2009.