An experiment was performed to compare the fracture toughness of high-purity 18 Ni maraging steel with commercial-purity steel of the same type (Corrosion Science, 1971: 723-736). For m = 32 specimens, the sample average toughness was  = 65.6 for the high purity steel, whereas for n = 38 specimens of commercial steel = 59.8. Because the high-purity steel is more expensive, its use for a certain application can be justified only if its fracture toughness exceeds that of commercial purity steel by more than 5. Suppose that both toughness distributions are normal.
a. Assuming that σ1 = 1.2 and σ2 = 1.1, test the relevant hypotheses using α = .001.
b. Compute b for the test conducted in part (a) when µ1 = µ2 = 6.