Task: Question Answering
Input (English): Problem: a , b and c can do a piece of work in 24 days , 30 days and 40 days respectively . they began the work together but c left 4 days before the completion of the work . in how many days was the work completed ? 
Options: a ) 33 , b ) 77 , c ) 66 , d ) 11 , e ) 99
Output (English): d