Can you explain how to solve this math problem: 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?