Task: Question Answering
Input (English): Problem: a factory has three types of machines , each of which works at its own constant rate . if 7 machine as and 11 machine bs can produce 470 widgets per hour , and if 8 machine as and 22 machine cs can produce 600 widgets per hour , how many widgets could one machine a , one machine b , and one machine c produce in one 8 - hour day ? 
Options: a ) 400 , b ) 475 , c ) 550 , d ) 560 , e ) 700
Output (English): d