Task: Question Answering
Input (English): Problem: john and andrew can finish the work 9 days if they work together . they worked together for 6 days and then andrew left . john finished the remaining work in another 6 days . in how many days john alone can finish the work ? 
Options: a ) 30 days , b ) 60 days , c ) 18 days , d ) 80 days , e ) 90 days
Output (English): c