Justin needs to collect one flower for each classmate that is in his 2nd-grade class. It takes him on average 10 minutes to find a flower he likes. He has been gathering for 2 hours. Assuming he has lost 3 of the flowers he initially gathered, how many more minutes does he need to look if he has 30 classmates?
Please reason step by step, and put your final answer within \boxed{}.
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