Specification for the diameter of a metal shaft is much wider than the machine used to make tire shafts is capable of. Consequently, the decision has been made to allow the cutting tool to wear a certain amount before replacement. The tool wears at the rate of .004 centimetre per metal shaft produced. The process has a natural variation, cr, of .01 centimetre and is Normally distributed. Specification for tire diameter of the metal shafts is 15.0 to 15.2 centimetres. How many shafts can the process turn out before tool replacement becomes necessary (i.e., before the process makes an out-of-spec shaft)? (See diagram below.)

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15.2 cm Upper specificction limit Three Sigma 15.0 cm. Lower specification limit Ö Number of shatts 0