With U.S. Department of Energy data for selected years from 2000 and projected to 2030, sulphur dioxide emissions from electricity generation (in millions of short tons per year) can be modeled by

E(x) = 0.0112x² + 0.612x + 11.9

where x is the number of years past 2000. Use n = 10 equal subdivisions and right-hand endpoints to approximate (to the nearest unit) the area under the graph of E(x) between x = 15 and x = 25. What does this area represent?