Suppose that two firms are competing on price. The firms produce identical goods, and the marginal cost of each firm is constant at $15. If one firm is charging a price of $18, the other firm should:

a. Charge a price of $15
b. Raise its price to $18.01
c. Cut is output to raise the market price well above $18
d. Also charge $18
e. Charge a price of $17.99