Task: Question Answering
Input (English): Problem: some consecutive natural numbers , starting with 1 , are written on the board . now , one of the numbers was erased and the average of the remaining numbers is 800 / 39 . find the number which was erased . 
Options: a ) 20 , b ) 87 , c ) 266 , d ) 288 , e ) 11
Output (English): a