Task: Question Answering
Input (English): Problem: 8 machines , each working at the same constant rate , together can complete a certain job in 24 days . how many additional machines , each working at the same constant rate , will be needed to complete the job in 16 days ? 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 6 , e ) 8
Output (English): c