total of 80 sixth grade students and 2 teachers from a certain school went to the spring outing in AD. The school only prepared 180 bottles of soft drinks. The director of general affairs explained to the teacher that each person will be provided with 3 bottles of soda (including the teacher), and the insufficient part can be purchased in the park, and will be reimbursed after returning to school. When you arrive at the park, there is a notice posted in the store: Every 5 empty bottles can be exchanged for a bottle of soda. So everyone is asked to return the empty bottles after drinking the soda, and the teacher will return them uniformly. Then use the best method to plan, at least how many bottles of soda to buy and go back to school for reimbursement.
某校六年级的80名同学与2名老师共82人去公元春游，学校只准备了180瓶汽水．总务主任向老师交待，每人供应3瓶汽水(包括老师)，不足部分可到公园里购买，回校后报销．到了公园，商店贴有告示：每5个空瓶可换一瓶汽水．于是要求大家喝完汽水后空瓶由老师统一退瓶．那么用最佳的方法筹划，至少还要购买多少瓶汽水回学校报销．
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