Jane Chang is making plans for a summer vacation. She will take $1,000 with her in the form of travelers checks. From the newspaper, she finds that if she purchases the checks by May 31, she will not have to pay a service charge. That is, she will obtain $1,000 worth of travelers checks for $1,000. But if she waits to buy the checks until just before starting her summer trip, she must pay a 1% service charge. (It will cost her $1,010 for $1,000 of travelers checks.) Jane can obtain a 13% interest rate, compounded weekly, on her money. How many weeks after May 31 can she begin her trip and still justify buying the travelers checks on May 31?