How many different spheres of radius $r$ can be drawn which touch all the three coordinate axes?

If $A$ and $B$ are the points $(3, 4, 5)$ and $(-1, 3, -7)$ respectively,find the equation of the set of points $P$ such that $PA^{2} + PB^{2} = k^{2}$,where $k$ is a constant.

If $(2, 3, 5)$ is one end of a diameter of the sphere ${x^2} + {y^2} + {z^2} - 6x - 12y - 2z + 20 = 0$,then the coordinates of the other end of the diameter are:

The equation of the sphere touching the three coordinate planes is

The shortest distance from the origin to a variable point on the sphere $(x-2)^2+(y-3)^2+(z-6)^2=1$ is

$A$ plane passes through a fixed point $(p, q, r)$ and cuts the axes at $A, B, C$. Then the locus of the centre of the sphere $OABC$ is