An increasing annuity-immediate makes the annual payments K, 2K, ..., 10K in years 1 through 10 at an annual effective interest rate of 7% and annual payments of 10K(1.05), 10K(1.05)^2, ...., 10K(1.05)^10 in years 11 through 20 at an annual effective interest rate of 5%. Given that the present value of annuity is $50,000 find K