Task: Question Answering
Input (English): Problem: for every even positive integer m , f ( m ) represents the product of all even integers from 2 to m , inclusive . for example , f ( 12 ) = 2 x 4 x 6 x 8 x 10 x 12 . what is the greatest prime factor of f ( 26 ) ? 
Options: a ) 23 , b ) 19 , c ) 17 , d ) 13 , e ) 11
Output (English): d