Let suppose 4parts of encyclopedia as one . Now, we have 22space to put these 4parts
We can select like : 22C1 +22C2 +22C3 +22C4
Now to have same order :
Case 1 : one place is chosen to put 4parts, so this can be done only in one way . Say ABCD
Case 2 : Two place is chosen . This can be done in 3ways. i. e, (A )(BCD) or (AB)(CD) or (ABC) (D)
case 3: Three place chosen.
A B CD or AB C D or A BC. D
Case4: 4place is chosen. This can be done in one way.
Therefore, total ways = 22C1×1 +22C2×3 +22C3×3+ 22C4×1