If the businessman were to evaluate the performance of his employees who produce part X then the employees would probably feel the need to work faster and harder. Since part X is very easy to produce employees would not feel threatened to make a mistake and mess the part up. They would be able to produce the parts quickly and easily since it would take little thought to put the pieces together, and since they are being evaluated they would want to perform better comparatively.
If he were to not evaluate the performance of his employees who produce part X then the employees would feel no need to work fast. They would still be able to produce the parts with out mistakes since the task is easy, but not as many parts would be produced because the employees would feel no pressure to perform as well as others around them.
If he were to evaluate the performance of his employees who produce part Y then the employees would feel an urgency to work at a faster pace. Since part Y is very difficult to produce the urgency that drives the employees would probably cause them to mess up and produce faulty parts. They would