The salesperson appears to have made effective use of b. foot-in-the-door phenomenon.
Explanation:
Foot-in-the-door phenomenon is a tactics used by many of the salesperson to sell their products. Under this technique, they make a customer to agree the large request by making them agree to their small request first.
Foot-in-the-door phenomenon was discovered by the psychologists Jonathan Freedman and Scott Fraser, when they met pedestrian salesmen at their heyday.
In the above scenario, the salesman visits my house and gave some free sample of cleaning liquid to try. He returns back in a week and requests to buy expensive cleaning products. This shows that the salesperson is following foot-in-the-door phenomenon.
