Given the task definition and input, reply with output. Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Problem: a certain car can travel 32 kilometers on a liter of fuel. if the fuel tank ' s contents decrease by 3.9 gallons over a period of 5.7 hours as the car moves at a constant speed, how fast is the car moving, in miles per hour ? ( 1 gallon = 3.8 liters; 1 mile = 1.6 kilometers )
Options: a. 52, b. 65, c. 78, d. 91, e. 104
a