Hello, I have a tricky question that I can't answer alone. Could you help me ?

A group of 9 consumers are trying to decide whether to connect to a new communications network. Consumer 1 is of type 1, consumer 2 of type 2, consumer 3 of type 3, and so on. Each consumer's willingness to pay to belong to the network is proportional to the number of consumers who belong. Where k is the number of consumers who belong, the willingness to pay of a type n consumer is equal to k times n. What is the highest price at which 7 consumers could all connect to the network and either make a profit or at least break even?

Select one:

a.$23

b.$26

c.$19

d.$21

e.$18