Task: Question Answering
Input (English): Problem: a owner of a mart earns an income of re 1 on the first day of his business . on every subsequent day , he earns an income which is just double of that made on the previous day . on the 10 th day of business , he earns an income of : 
Options: a ) 18 , b ) 21 , c ) 22 , d ) 20 , e ) 30
Output (English): a