Mr. Been invest R 20 000 at his local bank. It was agreed by the respective parties that the term of this investment will be 4 years and 7 months and that he will receive a single payment at the end of this term. Initially interest on this investment was calculated at an effective rate of 13.5% per annum. After 36 months, the bank changed their policy concerning the interest rate so that for the remainder of the term interest has to be calculated at a rate of 13.5% per annum compounded monthly. What amount of interest will Mr. Been receive from his investment?