Task: Question Answering
Input (English): Problem: a can do a piece of work in 8 days . b can do it in 16 days . with the assistance of c they completed the work in 4 days . find in how many days can c alone do it ? 
Options: a ) 87 days , b ) 20 days , c ) 26 days , d ) 19 days , e ) 16 days
Output (English): e