I have a question on stoneskin as a Paladin

1) If the whm has just cast a fresh stoneskin on me, will the stoneskin that ai cast override the whm's?

2) If I had just cast a fresh stoneskin on myself, will the whm's stoneskin override mine?

3) If the whm had cast a stoneskin on me and this stoneskin had absorbed some damage such that the remaining damage that it can absorb is less than the damage that a fresh stoneskin cast by either me oe a whm, will a new stoneskin cast by me or the whm override the existing stoneskin?