Gretchen invests 5000 dollars in a mutual fund on January 1. On March 1, she learns that her fund balance is 3400 dollars, and she then withdraws 1300 dollars. On August 1, her fund balance is 7400 dollars, and she then deposits 1000 dollars. On the following January 1, her fund balance is 6600 dollars. What is Gretchen's dollar-weighted rate of return? (Assume simple interest and months of equal length.)