Wally invests 6000 dollars in a mutual fund on January 1. On June 1, his fund balance is 3800 dollars. Wally doesn't notice the decline, and invests an additional 1000 dollars. On September 1, his fund balance is 9000 dollars. He then withdraws 1000 dollars. On the following January 1, his fund balance is 7700 dollars. What is Wally's time-weighted rate of return?