Task: Question Answering
Input (English): Problem: machine a produces 100 parts twice as fast as machine b does . machine b produces 100 parts in 80 minutes . if each machine produces parts at a constant rate , how many parts does machine a produce in 20 minutes ? 
Options: a ) 60 , b ) 80 , c ) 70 , d ) 40 , e ) 50
Output (English): e