A movie theater company is advertising a deal of a movie ticket, a bucket of popcorn, a drink, and a box of candy for $20. Normally, a movie ticket costs $8, a bucket of popcorn costs three dollars less, a drink costs a dollar more than popcorn, and a candy costs half as much as a drink. How many dollars does the deal save a customer who buys a ticket, popcorn, drink, and candy normally?
Please reason step by step, and put your final answer within \boxed{}.
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