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In a supply firm for the automotive industry one machine works irregularly ever now and then. Every time when this is the case the operator of the machine needs to rework the faulty pieces by hand. In case of irregularity the machine produces on average 6 faulty parts per shift with a variance of 4 (standard deviation = 2). The operator can handle a reworking effort of 5 parts per shift within his regular working hours. What is the probability that the operator needs to do overtime in case the machine works irregularly? (Assume normal distribution.) 30.85% 69.15% 59.87% 40.13%