1. Simple Annuities

A loan of $20,000 is to be repaid by annual payments of$4,000 per annum for the 1st 5yrs, and payments of \$4500 per yr thereafter for as long as necessary. Assuming that the effective rate of interest is 18%,

Determine: a. The total number of payments. ; b. The amount of the smaller final, made one year after the last regular payment.

I am not sure of the exact working, since there's an eff rate of interest as well, its confusing me.