You definitely are kidding us oO
The plane is imaginary, it assumingly starts at 0|0 and expands along the X and Y axis but stays 0 along the Z axis. Then an arbitrary point on this plane would be 0|0|0.
The normal of your imaginary plane is probably 0|0|1 since your plane faces upwards.


Shitlord by trade and passion. Graphics programmer at Laminar Research.
I write blog posts at feresignum.com