At an annual interest rate of i, i ≥ 0, the present
value of a perpetuity paying 10 at the end of each three-year
period, with the first payment at the end of year 3, is 34.21. At
the same annual effective rate of i, the present value of
a perpetuity paying 1 at the end of each four-month period, with
the first payment at the end of four months, is X.
Calculate X.