Asomatic cell of a ferret contains 40 chromosomes. how many will it have after mitosis?

40

Explanation:

In a mitotic cell division, the number of chromosomes remains constant. It is so because the chromosomes are replicated to produce chromatid which during cell division is equally distributed in all the daughter cells thereby preserving the chromosome number.  

For instance - if the somatic cell has 40 chromosomes then these chromosomes will duplicate to produce 80 chromatid. After the cell division, two daughter cells will be formed with each having 40 chromosomes.