A school is organizing a field trip and needs to determine the average cost per student. There are three grades participating: 7th grade with 40 students, 8th grade with 35 students, and 9th grade with 30 students. The total cost for the 7th grade is $800, for the 8th grade is $1050, and for the 9th grade is $1200. What is the average cost per student for the field trip? Let's think step by step and output the final answer within \boxed{}.
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