Interpolated Plane from 4 points

Hi all,

I'm trying to interpolate a plane based upon 4 points in 3d space.  I'm trying to model something for this, without success so far.

Understand that 3 points make a plane, but if I had 4 corners that vary in height, how could I use those points to best fit a plane?

Thoughts?

Thanks,

Mike

SolidworksSketching