Task: Question Answering
Input (English): Problem: a and b can do a piece of work in 45 days and 40 days respectively . they began to do the work together but a leaves after some days and then b completed the remaining work in 23 days . the number of days after which a left the work was ? 
Options: a ) 12 , b ) 11 , c ) 10 , d ) 9 , e ) 8
Output (English): d