Tony's dad is very strict about the washing machine and family members are only allowed to wash 50 total ounces of clothing at a time. Tony doesn't want to break the rules, so he weighs his clothes and finds that a pair of socks weighs 2 ounces, underwear weighs 4 ounces, a shirt weighs 5 ounces, shorts weigh 8 ounces, and pants weigh 10 ounces. Tony is washing a pair of pants, 2 shirts, a pair of shorts, and 3 pairs of socks. How many more pairs of underwear can he add to the wash and not break the rule?
Please reason step by step, and put your final answer within \boxed{}.
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