Betty Knight is planning to retire in 25 years, at which time she hopes to have accumulated enough money to receive an annuity of $30,000 a year for 20 years of retirement.  During her pre-retirement period she expects to earn 5 percent compounded annually. During retirement she expects to earn 4 percent compounded annually on her money.  What annual contribution to her retirement fund is required to meet her objective of having $30,000 a year for 20 years during retirement?