Task: Question Answering
Input (English): Problem: a certain protective additive increases from 30 days to 60 days the time between required maintenance checks on an industrial vehicle . by what percent is the time between maintenance checks increased by using the additive ? 
Options: a ) 25 % , b ) 33 1 / 3 % , c ) 100 % , d ) 66 2 / 3 % , e ) 75 %
Output (English): c