$A$ person has three different bags and four different books. The number of ways, in which he can put these books in the bags so that no bag is empty, is:

Three letters are to be sent to different persons,and addresses on the three envelopes are also written. Without looking at the addresses,the probability that all the letters go into the right envelopes is equal to

There are $4$ balls of different colors and $4$ boxes of the same colors. In how many ways can the $4$ balls be placed in the boxes,one in each box,such that no ball goes into a box of its own color?

The number of ways of dividing $52$ cards amongst four players equally is

The number of ways of dividing $200$ dissimilar things into $10$ groups each containing $20$ elements is

Three letters are placed at random into three envelopes addressed to three different people. The probability that all letters are placed in the correct envelopes is ..........