The event that would prompt you to reverse your decision to choose Cancun over Fort Lauderdale for spring break is: b. The marginal cost of going to Fort Lauderdale decreases. This means if the cost of traveling to Fort Lauderdale becomes significantly lower, it could make Fort Lauderdale a more attractive option compared to Cancun, leading you to reconsider and possibly switch your destination

. In contrast, a decrease in the cost of Cancun or an increase in the benefit of Cancun would reinforce your original choice, and a decrease in the benefit of Fort Lauderdale would make it less appealing, so these would not prompt a reversal.