Please do not use excel

A loan L is repaid using increasing payments. The first payment, made at t = 1, is of amount 200, and each subsequent payment increases by a factor of (1.55), with the last payment at t = 20. However, at t = 10, the borrower decides to make an additional payment of X, which allow him to halve the size of the remaining payments (t = 11,..., 20). Determine L and X if the effective interest is 8%