Give an example of a relationship type between two entity types where an attribute can be assigned to the relationship

QUESTION:

Give an example of a relationship type between two entity types where an attribute can be assigned to the relationship type instead of to one of the two entity types?

SOLUTION:

A good example involves the situation in Exercises 26 and 27 below, where the attribute commission is defined as the commission received by an insurance agent for the sale of a policy to a client. Another example could involve a relationship such as the following: