Refer to the comparison of the daily adult intake of selenium in two different regions of the United States in Exercise 8.45. Suppose you wish to estimate the difference in the mean daily intakes between the two regions correct to within 5 micrograms, with probability equal to .90. If you plan to select an equal number of adults from the two regions (i.e., n1 = n2), how large should n1 and n2 be?