Task: Question Answering
Input (English): Problem: one copy machine can make 30 copies a minute , and a second copy machine makes 15 copies a minute . if the two copiers work together , how long would it take them to make 900 copies ? 
Options: a ) 15 minutes , b ) 20 minutes , c ) 25 minutes , d ) 30 minutes , e ) 35 minutes
Output (English): b