$10$
5. Uncle Li rents a piece of farmland, he pays the landowner 1000 yuan in cash and 2 bags of corn as rent. If the price of corn is 1 yuan per pound, the rent per acre is 180 yuan; if the price of corn is 1.5 yuan per pound, the rent per acre is 220 yuan. The area of the farmland Uncle Li rents is $\qquad$ acres.