There are $4$ parcels and $5$ post-offices. In how many different ways can the registration of the parcels be made?

$A$ question paper is divided into two parts $A$ and $B$,and each part contains $5$ questions. The number of ways in which a candidate can answer $6$ questions by selecting at least two questions from each part is:

In a plane,there are $10$ points,out of which $4$ are collinear. The number of triangles that can be formed by joining these points is:

If $^{56}P_{r+6} : ^{54}P_{r+3} = 30800 : 1$,then $r = $

An urn contains $5$ red marbles,$4$ black marbles,and $3$ white marbles. The number of ways in which $4$ marbles can be drawn so that at most three of them are red is:

Find the total number of $9$ digit numbers which have all the digits different.