The Bank of Fast Loans uses the following rating scheme to classify the riskiness of its customers. Risk Class Prime High grade Upper medium grade | Lower medium grade Speculative: Non-investment grade Speculative: Highly Substantial risks Extremely speculative Risk Premium (%) 05 10 1.5 20 40 6.0 9.0 12.0 The bank's pure rate of interest is 2% and the inflation premium is 3.5%. The bank offers an annual rate of 9.79% to a customer. What is the risk class of this customer? A. Upper medium grade B. Substantial risks C.Speculative: Highly D. Lower medium grade E.High grade O F. Speculative: Non-investment grade