Write some Software Repayment Calculator

Need the following very simple stuff I just cant do it. NEEDS TO BE ABLE TO WORK IN SHOPIFY PLEASE SEE IMAGE AS AN EXAMPLE When you move the slider on the Price the monthly repayment must adjust accordingly Low risk = 15% Med Risk = 17% High risk = 20% Intreset rate based on months R20,000-R49,999 = 48 months R50,000-R100,000 = 60 months R100,000 - R150,000 = 72 months