Harvard business school started using case studieslong dashdescriptions of strategic problems encountered at real companieslong dashin their courses in 1912. today, harvard business publishing (hbp) sells its case studies to about 4,000 colleges worldwide. hbp is the sole publisher of the harvard business school's case studies. what criteria would you use to determine whether hbp has a monopoly on the sale of business case studies to be used in college courses? a. the persistence of economic profits, the availability of close substitutes, and a high price elasticity of demand. b. the ability to ignore the actions of other firms, the persistence of economic profits, and the availability of close substitutes. c. the availability of any substitutes, the ability to set prices, and the persistence of normal profits. d. the ability to set prices, the persistence of economic profits, and the availability of any complements.