Two mating parts have critical dimensions x1 and x2 as shown in the figure. Assume that x1 and x2 are normally distributed with means 1 and 2 and standard deviations 1 = 0.400and 2 = 0.300. If it is desired that the probability of a smaller clearance (i.e., x1 − x2) than 0.09 should be 0.006, what distance between the average dimension of the two parts (i.e., 1 − 2) should be specified by the designer?