equation of a plane touching a sphere

I need to find the equation for a plane that just touches a sphere (x - 4)^2 + (y + 1)^2 + (z - 3)^2 = 4 that is parallel to the xy plane

In writing this I think I would just set x and y to zero and solve for z and therefore z = 5 would be the answer. Could someone please confirm this for me??

So, if this were to be parallel to the zy plane then I would just solve for x with z and y at 0, Right? IN that case x would = 2

THanks so much for all the assistance you folks have provided, it really helps. Frostking