Task: Question Answering
Input (English): Problem: there has been successive increases of 25 % and then 15 % in the price of gas from the previous month . by what percentage should a driver reduce gas consumption so that the expenditure does not change ? 
Options: a ) 30 % , b ) 50 % , c ) 66.66 % , d ) 15 % , e ) 75 %
Output (English): a