Johnny is a dog walker. He can walk 3 dogs at once. He gets paid $15 for a 30-minute walk and $20 for a 60-minute walk. Johnny works for 4 hours per day. If he always walks the maximum number of dogs possible and 6 dogs have 60-minute walks per day, how much money does he make in a week where he works 5 days?
Please reason step by step, and put your final answer within \boxed{}.
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