Tony drives a car that gets 25 miles to the gallon.  He drives 50 miles round trip to work 5 days a week.  His tank holds 10 gallons.  He begins the week with a full tank and when he runs out he fills up at the local gas station for $2 a gallon.  How much money does Tony spend on gas in 4 weeks?
Please reason step by step, and put your final answer within \boxed{}.
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