Task: Question Answering
Input (English): Problem: a certain sum is invested at simple interest at 18 % p . a . for two years instead of investing at 12 % p . a . for the same time period . therefore the interest received is more by rs . 504 . find the sum ? 
Options: a ) 7000 , b ) 7029 , c ) 2778 , d ) 4200 , e ) 2791
Output (English): d