Grade 11 - Applied Mathematics (IGCSE) - A man borrows 5000 at 12% compound interest per annum,

Grade 11 - Applied Mathematics (IGCSE) - A man borrows 5000 at 12% compound interest per annum, interest payable after six months. He pays back 1800 at the end of every six months. Calculate the third payment he has to make at the end of 18 months in order to clear the entire loan.