Condition for Two Lines to Parallel

Q. If any tangent plane to the sphere $(x-a{)}^2+(y-b{)}^2+(z-c{)}^2=r^2$ makes intercepts $a,b,c$ with the coordinate axes at $A,B,C$ and $P$ be the center of the sphere. Then

1. $\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}=\frac{4}{r^2}$
2. $\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}=\frac{1}{r^2}$
3. Volume of the tetrahedron $PABC=\frac{abc}{3}$
4. Volume of the tetrahedron $PABC=\frac{abc}{6}$

Q. If any tangent plane to the sphere $(x-a{)}^2+(y-b{)}^2+(z-c{)}^2=r^2$ makes intercepts $a,b,c$ with the coordinate axes at $A,B,C$ and $P$ be the center of the sphere. Then

1. $\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}=\frac{4}{r^2}$
2. $\frac{1}{a^2}+\frac{1}{b^2}+\frac{1}{c^2}=\frac{1}{r^2}$
3. Volume of the tetrahedron $PABC=\frac{abc}{3}$
4. Volume of the tetrahedron $PABC=\frac{abc}{6}$