People hired milk shakes for two very different jobs during the day, in two very different circumstances. Each job has a very different set of competitors--in the morning it was bagels and protein bars and bottles of fresh juice, for example; in the afternoon, milk shakes are competing with a stop at the toy store or rushing home early to shoot a few hoops--and therefore was being evaluated as the best solution according to very different criteria. This implies there is likely not just one solution for the fast-food chain seeking to sell more milk shakes. There are two. A one-size-fits-all solution would work for neither.