Task: Question Answering
Input (English): Problem: each machine of type a has 2 steel parts and 2 chrome parts . each machine of type b has 6 steel parts and 5 chrome parts . if a certain group of type a and type b machines has a total of 20 steel parts and 22 chrome parts , how many machines are in the group 
Options: a ) 2 , b ) 3 , c ) 4 , d ) 6 , e ) 7
Output (English): e