I am trying to solve this question by intupting the N, I/Y, PV, PMT, FV on my ba ii plus calculator please. The correct answer is between 7-8 years but I need to know how to do this way.

18. William wishes to save enough money to purchase a retirement lake cabin. He is willing to spend $200,000 for the cabin and he can save $20,000 per year and invest the money into an account earning 7.00% per year. If his investments come in the form of equal annual end-of-the-year cash flows and the first cash flow is in exactly one year, how long will it take him to save enough money to buy the lake cabin