pacmandefense

As a follow on here. I struggled with my baII on saturday with one of these q's! Seems silly but couldnt punch it out. In example above. I simply use CF0 -1mill , CF1-CF9 0 and CF10 as 20 mill. 1/y 15. N 10. didnt get correct answer....clearly manula calc is straighfoward buy For my education what have I done wrong? Il be review TVM tonight thats for sure!