A local bank is running the following advertisement in the​ newspaper: "For just $ $2,000 we will pay you $140 ​forever!" The fine print in the ad says that for a $2,000 ​deposit, the bank will pay $140 every year in​ perpetuity, starting one year after the deposit is made. What interest rate is the bank advertising​ (what is the rate of return of this​ investment)?