Hard Nails and Bright Nails are competing nail salons. Both companies have the same number of customers. Both charge the same price for a manicure. The only difference is that Hard Nails pays its manicurists on a salary basis (i. e., a fixed cost structure) while Bright Nails pays its manicurists on the basis of the number of customers they serve (i. e., a variable cost structure). Both companies currently make the same amount of net income. If sales of both salons increase by an equal amount, Hard Nails

a. will earn a higher profit than Bright Nails
b. will earn a lower profit than Bright Nails
c. will earn the same amount of profit as Bright Nails
d. The answer cannot be determined from the information provided.