Vicky's Costume Shop is gearing up for Halloween, which is typically their busiest time of the year. Vicky was able to secure 13,000 costumes for the holiday this year. Vicky sells individual costumes for $40 and couples costumes for $70. The cost per costume for Vicky is $30. Typically half of all costumes are sold individually and half in pairs for couples costumes, however on Halloween the majority of costumes are sold as part of couples costumes. Last year Vicky made $85,000 over the Halloween season, and hopes to make the same profit this year. Assuming Vicky is able to sell all of her inventory, what is the maximum proportion of costume sales that can come from couples costumes in order for Vicky to earn a profit of $85,000?