NoNox Industries is examining its capital structure with the intent of arriving at an optimal debt ratio. It currently has no debt and has a beta of 0.87. The riskless interest rate is 5.00%, and the market risk premium (MRP) is 5.5%. Your research indicates that the debt rating will be as follows at different debt levels: DID+E) Rating Tax rate AAA AA A BBB Interest Rate 5.20% 5.50% 6.25% 7.00% 10.00% 10.00% 11.00% 12.50% 12.50% 12.50% 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% BB 35% 35% 35% 35% 35% 30.05% 22.76% 17.17% 15.02% 13.36% B CCC CC D The firm currently has 5 million shares outstanding at $25.75 per share. What is the firm's optimal debt ratio? O a. 35%. O b. 40%. O c. 45%. O d. 50%. e. None of the above. 6C Cloudy