Answer: all integers from 1 to 6 inclusive
Step-by-step explanation: it says that "He can't purchase partial boxes" so it cant be all real numbers from 1 to 6 inclusive, and it's not all real numbers because he is limited to only 6 boxes. and it's just not {250,450,650,850,1050,1300}. so that leaves all integers from 1 to 6 inclusive.