Task: Question Answering
Input (English): Problem: machine a produces 100 parts twice as fast as machine b does . machine b produces 100 parts in 20 minutes . if each machine produces parts at a constant rate , how many parts does machine a produce in 8 minutes ? 
Options: a ) 100 , b ) 90 , c ) 80 , d ) 30 , e ) 50
Output (English): c