Task: Question Answering
Input (English): Problem: a person borrows rs . 4000 for 2 years at 4 % p . a . simple interest . he immediately lends it to another person at 6 p . a for 2 years . find his gain in the transaction per year . 
Options: a ) 100 rs , b ) 80 rs , c ) 160 rs , d ) 180 rs , e ) 200 rs
Output (English): b