Accounting for the cash discount period and for the credit period, what is the optimal cash discount percentage ? Answer this question by solving for the discount rate that sets the present value of full price equal to the present value of the discounted price. The discounted price is received at the end of the cash discount period. The full price is received at the end of the credit period. (do not use the Hill-Reiner method)

-cash discount period 10 days

-credit period 53 days

-annual cost of capital 20 %

Express your answer as a decimal (example: if your answer is 4.3% then enter it as 0.043).