On January 1, 2014, a company has assets of $15.40 billion and stockholders' equity of $8.60 billion. On January 1, 2015, the same company has assets of $19.40 billion and stockholders' equity of $9.60 billion. During 2014, the company had total sales revenue of $9.60 billion and total expenses of $6.40 billion. The company's debt-to-assets ratio on January 1, 2015 is: