Task: Question Answering
Input (English): Problem: john has exactly 31 pens , and each pen is either bule , black , or red . if he has 5 more black pens than red pens , and twice as many blue pens as black pens , how many blue pens does john has ? 
Options: a ) 15 , b ) 18 , c ) 20 , d ) 22 , e ) 17
Output (English): b