Herring Corporation has operating income of $235,000 and a 40% tax rate. The firm has short-term debt of $115,000, long-term debt of $321,000, and common equity of $436,000. What is its return on invested capital? 

a. 17.42% 

b. 16.17% 

c. 14.92% 

d. 15.50% 

e. 18.27%