Sun Do sells key chains with leather fobs for $12 and $9. The key chains are very similar and have identical manufacturing costs. The difference is that the stitching on the leather fob is in a less precise pattern on the $9 key chain than it is on the $12 key chains. What approach to price discrimination is Sun Do using

Statistical process control charts: a. indicate to the operator the true quality of material leaving the process. b. display upper and lower limits for process variables or attributes and signal when a process is no longer in control. c. indicate to the process operator the average outgoing quality of each lot. d. display the measurements on every item being produced. e. are a graphic way of classifying problems by their level of importance, often referred to as the 80-20 rule.