The data from the u. s. census bureau for 1982−2003 shows that the surface area of the united states that is covered by rural land can be modeled by the function r(x) = 0.003x3 − 0.086x2 − 1.2x + 1,417.4 where x is the number of years after 1982 and r(x) is the surface area in millions of acres. the total surface area of the united states can be modeled by the function t(x) = 0.0023x3 + 0.034x2 − 5.9x + 1,839.4 where x is the number of years after 1982 and t(x) is the surface area in millions of acres.