Task: Question Answering
Input (English): Problem: the average mark of the students of a class in a particular exam is 65 . if 5 students whose average mark in that exam is 20 are excluded , the average mark of the remaining will be 90 . find the number of students who wrote the exam . 
Options: a ) 14 , b ) 25 , c ) 35 , d ) 45 , e ) 55
Output (English): a