John secured a loan of R21000 for his studies at the beginning of this year. The rate of interest is 8% p.a. compounded quarterly for the first 4 years during his studies and i^(12)=13% p.a. thereafter. He must repay the loan with 3 payments: RX at the beginning of the 6th year and R2X at the beginning of each of the 7th and 8th years.

a) Find the amount of each of the three payments.