Task: Question Answering
Input (English): Problem: a certain fraction is equivalent to 2 / 5. if the numerator of the fraction is increased by 4 and the denominator is doubled, the new fraction is equivalent to 1 / 3. what is the difference of the numerator and denominator of the original fraction ?
Options: a. 49, b. 9, c. 28, d. 26, e. 21
Output (English): b