Task: Question Answering
Input (English): Problem: the average marks of a class of 30 students is 40 and that of another class of 50 students is 90 . find the average marks of all the students ? 
Options: a ) 71.25 , b ) 52.9 , c ) 52.1 , d ) 52.3 , e ) 42.5
Output (English): a