Normal distribution of heights

The heights of U.S. men are normally distributed with a mean of 69 in and a standard deviation of 3 in. This means that the fraction of men with a height between a and b (with a)inches is given by the integral

What percentage of American men are between 66 and 72 inches in height? Use the method of your choice and experiment with the number of subintervals until you obtain successive approximations that differ by less than 10−3.