Use reasoning to lead to the answer of the following question:
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?

1500
Johnny spends 6 / 3 = 2 hours walking the 6 dogs who have 60 - minute walks.

He makes $20 * 6 = $120 for these walks.

Thus, he has 4 - 2 = 2 hours = 120 minutes left to walk the other dogs.

He can walk 3 * (120 / 30) = 12 dogs in this time.

Thus, he will make $15 * 12 = $180 on these walks.

In total per day, he makes $120 + $180 = $300 per day.

Thus, during the week, he makes $300 * 5 = $1500.

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Thus, the answer is 1500