Blackie Knight is planning to retire in 25 years, at which time she hopes to have accumulated enough money to receive an annuity of $21,000 a year for 26 years of retirement. During her pre-retirement period she expects to earn 7 percent annually, while during retirement she expects to earn 6 percent annually on her money. What annual contributions to this retirement fund are required for Blackie to achieve her objective and sleep well at night?