A car rental company offers two types of rental packages. Package A charges a flat rate of $50 per day plus $0.20 per mile driven. Package B charges a flat rate of $70 per day plus $0.10 per mile driven. If a customer plans to rent a car for 3 days and drive a total of 150 miles, which package offers the better rate, and by how much? Let's think step by step and output the final answer within \boxed{}.
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