Vacation tours to Europe invariably package visits to disparate regions: cities, mountains, and the seaside. Bundling, a type of second degree price discrimination, is most profitable when: a. preference for the seaside is always higher than preferences for city excursions. b. no one wants to take a European vacation package to cities, mountains, and the seaside. c. preference rankings of vacationers travelling together are positively correlated. d. the preference rankings of vacationers travelling together are negatively correlated. e. a preference for cities is always higher than preferences for mountain vistas.