A solid cube whose edges are `12` cm each has been cut by a plane such that the plane bisects 3 edges meeting at a corner . The surface area of the remaining part of the cube after the small piece is removed will be:
a.   `81+10sqrt(3)`
b.   `810+10sqrt(3)`
c.   `810-10sqrt(3)`
d.   `810+18sqrt(3)`