Task: Question Answering
Input (English): Problem: working at their respective constant rates , machine a makes 100 copies in 8 minutes and machine b makes 150 copies in 10 minutes . if these machines work simultaneously at their respective rates for 30 minutes , what is the total number of copies that they will produce ? 
Options: a ) 250 , b ) 425 , c ) 675 , d ) 825 , e ) 750
Output (English): d