Professor Frei suggests there are five distinct forms of customer-introduced variability including in which customers can differ from one another with regard to the amount of effort they are willing to apply to certain tasks, even if they are capable of performing them.

Customers demand and expect different services outcomes, even from the same service provider.  

Explanation:

There are five variabilities in the form of customer introduction.  

The arrival variability The request variability The capability variability The effort variability The subjective preference variability

Thus here professor Frie suggests the variability related to customer subjective preference variability.

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Ifound the exercise on the internet. attached is the list mentioned above.in order for a compound to be considered optically active it can't have any axis or plan of symmetry. the molecule  shouldn't also  be superimposable on its mirror image.with such considerations, the compounds that are optically active are: -third compound on the first image is optically active; -second and third compound from the second image are optically actives.