Which of the following best defines the concept of Agency?

a$.$

The relationship between a marketing company and its marketers.

b$.$

None of the above.

c$.$

Agency is a relationship based on an express or implied agreement by which one person, the agent, is authorized to act under the control of and for another, the principal, in negotiating and making contracts with third persons.

d$.$

The relationship between a vendor of a product and the manufacturer of those products.