Task: Question Answering
Input (English): Problem: for a positive integer n , if 5 ^ n is a factor of 20 ! , but 5 ^ n + 1 is not a factor of 20 ! , what is the value of n ? 
Options: a ) 4 , b ) 6 , c ) 7 , d ) 8 , e ) 9
Output (English): a