Task: Question Answering
Input (English): Problem: a tank can supply water to a village for 100 days . if a leak at the bottom of the tank drains out 10 liters per day , the supply lasts for 75 days only . for how many days will the supply last if the leak drains out 20 liters per day ? 
Options: a ) 50 , b ) 60 , c ) 65 , d ) 70 , e ) 72
Output (English): b