The tensile strength of a welded joint used in construction has to be at least equal to 40 tons per square inch (ton/in.2). A random sample of 100 joints welded by a welding machine yielded the following estimates of the parameters of the distribution of the tensile strengths: Mean = 65 ton/in.. Standard deviation = 8.2 ton/in. Compute the Cp index and estimate the proportion of defectives generated by the machine, assuming that the distribution of the tensile strengths is normal.