Firms use price discrimination to increase their profits by converting part or all of consumer surplus to producer surplus. Which of the following market conditions is not necessary for a firm to engage in price discrimination?

a) A firm must have the ability to prevent arbitrage.

b) A firm must have the ability to hide their prices from consumers.

c) A firm must have the ability to separate consumers into groups based on their elasticities of demand.

d) A firm must have some market power.