BBK Enterprises borrowed $100,000. Half of the amount ($50,000) was obtained at 4% per year, and the other half at 10% per year. BBK can make payments on either half at its discretion. For example it could pay off the 4% loan first and then pay off the 10% loan. The only requirement is that the total yearly payment is the same amount each year. Find the minimum annual payment that will pay off both loans with 20 equal annual payments.