Karen, aged 55, must choose between two actuarially equivalent retirement options. Option I offers annual payments commencing at age 65; the initial payment will be 10,000 and each subsequent payment will be 4% greater than the previous one.

Alternatively, she can choose early retirement by picking Option II, which offers annual payments commencing immediately; the initial payment will be K and each subsequent payment will be 4% greater than the previous one. At 4%, we are given the values Ds5 = 150, Des = 80, N55 = 2000, Nes = 900, ^55 = 20, ees = 13. Find K.