Afin-Super is the largest superannuation and pension fund in Macquarieland. To promote pension and annuity service, Afin-Super is serving a short-term experience plan(STEP). Plan joiners will be paid $10,000 once a year for a 2-year period (2 payments in total). The first payment will come in 5 years from now.

The yield curve is flat at 5% for all maturity. Interests are compounded annually.

What is the Macaulay duration of STEP?