Refer to Exercise 10-52 regarding the proportion of carbon monoxide in exhaust gases, which has an upper specification limit of 0.30. If the average carbon monoxide content is 1 standard deviation below the upper specification limit, the devices should be rejected 5% of the time. If the average carbon monoxide content is 0.8 standard deviation above the upper specification limit the probability of acceptance should be 0.20. The standard deviation of the proportion of carbon monoxide is unknown. Find a variable sampling plan and describe its operation.