The inspection department in an automobile final assembly plant checks cars coming off the line against 85 features that are considered critical-to-quality characteristics for customer satisfaction. During a one-month period, a total of 16,578 cars were produced. For those cars, a total of 1,989 defects of various types were found, and the total number of cars that had one or more defects was 512. Determine
(a) The number of defects per million opportunities and corresponding sigma level,
(b) The number of defects per million and corresponding sigma level, and
(c) The number of defective units per million and corresponding sigma level.