Hi guys. Would be much appreciated if somebody could give me a start on this problem, I'm really stuck on it.

A washing machine, cash price $ 850 is available on the following terms:

A deposit of $ 100 followed by equal payments at the end of each month for the next 18 months.

If interest is 6% pa compounded monthly for the first 6 months and 8% pa compounded monthly thereafter, determine the size of the regular monthly payments.