Heisenberg owns a pharmacy. He earned a total of $80 from 100 mg amoxicillin and $60 from 500 mg amoxicillin every week. If each capsule of 100 mg amoxicillin costs $5 and each capsule of 500 mg amoxicillin costs $2, how many capsules of amoxicillin does he sell every 2 weeks?
Please reason step by step, and put your final answer within \boxed{}.
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