6. Scarcity, opportunity cost, and marginal analysis Kevin is training for a triathlon, a timed race that combines swimming, biking, and running. Consider the following sentence: Kevin has only 20 hours this week that he can devote to training. Each hour he spends swimming is an hour that he can't spend biking or running. Which basic principle of individual choice do these statements best illustrate? O People usually exploit opportunities to make themselves better off. O Kevin can use time most efficiently by spending the same amounts of time on swimming, biking, and running. O Kevin has an incentive to spend more time on swimming than on biking or running. O People face trade-offs