Task: Question Answering
Input (English): Problem: an empty fuel tank with a capacity of 200 gallons was filled partially with fuel a and then to capacity with fuel b. fuel a contains 12 % ethanol by volume and fuel b contains 16 % ethanol by volume. if the full fuel tank contains 28 gallons of ethanol, how many gallons of fuel a were added ?
Options: a. 160, b. 150, c. 100, d. 80, e. 50
Output (English): c