Task: Question Answering
Input (English): Problem: x can do a piece of work in 4 hours ; y and z together can do it in 3 hours , while x and z together can do it in 2 hours . how long will y alone take to do it ? 
Options: a ) 5 hours , b ) 10 hours , c ) 12 hours , d ) 24 hours , e ) 15 hours
Output (English): c