Suppose that the diameters of bearings are independently normally distributed random variables with mean=1.005 and variance=(.003)^2. The diameters of shafts are independent normally distributed random variables having mean=.995 and variance=(.004)^2. Let S be the diameter of a shaft taken at random and let B be the diameter of a bearing. a) what is the probability Pr(S>B) of interference? b) What is the probability of one or fewer interferences in 20 random shaft-bearing pairs?