premise: Over the course of one day, a landscaper will use a truck to haul exactly seven loads—three loads of mulch and four loads of stone. The truck's cargo bed will be cleaned in between carrying any two loads of different materials. To meet the landscaper's needs as efficiently as possible, the following constraints apply: The cargo bed cannot be cleaned more than three times. The fifth load must be mulch. Which one of the following must be true?
hypothesis: At least two loads of mulch are hauled consecutively.