Which of the following conditions must be satisfied for price discrimination to be successful? a. the seller must have a different product for each group of customers and must be able to prevent arbitrage between the groups b. the seller must be able to identify each customer as having a high or low value. c. the seller must be able to identify groups with differing elasticity of demand, must be able to prevent arbitrage, and must not face additional marginal cost to serve each group d. none of the above