For example, a tea shop sells a good brand of tea. For a cup of the tea, the competitive price (offered by many competitive suppliers) and the monopoly price (offered by few dominant suppliers) are $3.50 and $4 respectively. It is supposed that there are three customers to buy the tea, and the reservation price of these three customers are $6, $5 and $3.5 respectively. Based on the competitive market price ($3.5), their consumer surplus would be $2.5, $1.5 and $0 respectively. By using the first type of discrimination, the tea shop can ask different prices to these three customers which is $6, $5 and $3.5. By doing so the shop will sell three cups of the tea, and all consumer surplus ($4) would be captured. However, if the shop sets a single price $4, then it can only sell two cups of tea, and the third customer would be eliminated from service. Therefore, not only the profit is reduced but also the number of customers served is reduced as well. Although it sounds great that a company can increase their profits and the quantity of products sold as well as the number of customers serviced, in practice it is hard to conduct. There are two reasons: first, it is difficult to know each customer’s reservation price; second, in order to know customer’s reservation price, companies need a lot of efforts in marketing research and investigation, which adds extra cost to the product and then reduces the product’s profit. Therefore, it is more suitable for some professional people such as dentists, lawyers and accountants, as they know their customers relatively well. For example, a lawyer may offer a reduced service fee to low-income client, but may charge a higher service fee to upper-income clients as they have the ability to pay. The possible problem is some customers who pay higher price may object price discrimination and argue that it represents a transfer of consumer surplus from customers to companies, which benefits less to customers than to companies such resulting an unfairness to rich people.