Task: Question Answering
Input (English): Problem: four machines , each working at the same constant rate , together can complete a certain job in 12 days . how many additional machines , each working at the same constant rate , will be needed to complete the job in 8 days ? 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 6 , e ) 8
Output (English): a