In 2018, Caterpillar Inc. had about 652 million shares outstanding. Their book value was $27.0 per share, and the market price was $156.80 per share. The company's balance sheet shows that the company had $20.80 billion of long-term debt, which was currently selling near par value.

a. What was Caterpillar's book debt-to-value ratio? (Do not round intermediate calculations. Enter your answer as a decimal rounded to 2 decimal places.)

b. What was its market debt-to-value ratio? (Do not round intermediate calculations. Enter your answer as a decimal rounded to 2 decimal places.)

c. Which measure should you use to calculate the company's cost of capital?