[" Thattretion "6.37" A shelf contains "20" books of which "4" are "],[" single whume and the other form sets of "8,5," and "3" volumes."],[" Find the number of ways in which the books may be arranged "],[" on the shelf oo that "],[[" 1) wolumes of each setwill not be separated,"],[" W.wolumes of cach set remain in their due order."]]