When Billy was first hired, he was paid at a rate of $10 per hour.  After 2 months, he was given a raise of $0.50 per hour.  On his first anniversary at work, he was given a raise of $1.00 per hour.  Sally just started working at a different business, and her starting salary is $0.50 more per hour than Billy's starting salary was.  If both Billy and Sally work 20 hours, how much more money will Billy earn than Sally, in dollars?
Please reason step by step, and put your final answer within \boxed{}.
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