Task: Question Answering
Input (English): Problem: there are 10 books on a shelf , of which 4 are paperbacks and 6 are hardbacks . how many possible selections of 5 books from the shelf contain at least one paperback and at least one hardback ? 
Options: a ) 75 , b ) 120 , c ) 210 , d ) 246 , e ) 252
Output (English): d