10 persons are invited for a party In how many ways can they and the host be seated at a circular table?

If 20 persons were invited for a party, in how many ways can they and the host be seated at a circular table? In how many of these ways will two particular persons be seated on either side of the host?

20 persons were invited to a party. In how many ways, they and the host can be seated at a circular table?

20 persons are invited for a party.The different number of ways in which they can be seated on acircular table with two particular persons seated,on either side of the host is