If P > ATC at MC = MR, firms are..?

Answer Options:

a. Making an economic profit, and this is a signal for new firms to enter

b. Making an economic loss, and this is a signal for new firms to enter

c. Making an economic profit, and this is a signal for existing firms to exit

d. Making an economic profit, and no firms should enter or exit

e. Making an economic loss, and this is a signal for existing firms to exi