A firm's total revenue is $400 for 8 units of output, $600 for 12 units of output,

Question:

A firm's total revenue is $400 for 8 units of output, $600 for 12 units of output, and $1,100 for 22 units of output. Evidently this firm is operating in a(n):
a. Perfectly competitive market.
b. Monopolistically competitive market.
c. Oligopolistic market.
d. Monopolist market.
e. Monopolistic market.