At the end of year X, automobile installment credit accounted for 36% of all outstanding consumer installment credit. At that time automobile finance companies extended $57 billion of credit, or 1/3 of the automobile installment credit. How many billion dollars of consumer installment credit was outstanding at that time?  Choose the correct choice from the following options
A) 62 B) 171 C) 475 D) 513 E) 684

Rationale: "total automobile instalment credit = 57 * 3 = 171 total consumer instalment credit = 171 ∗ 100 / 36 = 475 ; answer = c . 475"
Answer: C