Beverly just finished her five-mile run and is now at the drugstore deciding on a beverage. She enjoys cola soda but feels like something lighter today. In the soda aisle she considers Sprite or 7-Up. To her they taste about the same, but she notices that Sprite is having a sale and she can get two for the price of one 7-Up can. She purchases the two Sprite cans and happily goes on her way. Beverly has just experienced a: a) substitute offering situation b)competitive offering situation c)competitive advantage situtation