A door-to-door hearing aid salesman specifically targets elderly clients. When the clients ask questions about the contract, the salesman is not truthful with them entirely. The answers to their questions are usually found on the tiny, hard-to-read print on the very back of the long contract the clients must sign. The salesman knows that his clients have poor vision and hearing, and uses this to his advantage in his sales techniques and with the small contractual terms. The scenario above is a possible example of which type of agreement?