The following table gives the the approximate amount of emissions, E, of nitrogen oxides in millions of metric tons per year in the US. Let t be the number of years since 1940 and E = t). 194019501960197019801990 t O 10 20 30 4O 50 E 6.5 8.9 12.6 18.2 20.5 19.3 Estimate the integral: L150 f(t)dt m C] Be sure that you know what the units of your answer are, and what its meaning is! (Original data from the Statistical Abstract of the US, 1992)