Task: Question Answering
Input (English): Problem: p , q and r together earn rs . 1620 in 9 days . p and r can earn rs . 600 in 5 days . q and r in 7 days can earn rs . 910 . how much amount does r can earn per day ? 
Options: a ) rs . 40 , b ) rs . 70 , c ) rs . 90 , d ) rs . 100 , e ) rs . 120
Output (English): b