[Gmsh] Define Physical Surface on Extruded Geometry

[Oka Kurniawan]

Hi,
I am a newbie in using Gmsh,

I am wondering whether we can define physical entities, such as
surface from an extruded surface.

Below is my .geo file

How can I define a Physical Surface on the 4 sides of the block?

Thanks.

lc=0.1;
Point(1)={0.,0.,0.,lc};
Point(2)={1.36,0.,0.,lc};
Point(3)={1.36,1.36,0.,lc};
Point(4)={0.,1.36,0.,lc};

Line(1)={1,2};
Line(2)={2,3};
Line(3)={3,4};
Line(4)={4,1};

Line Loop(5)={1,2,3,4};

Plane Surface(6)={5};

//extrude to create volume
out[]=Extrude {0,0,15} {
	      Surface{6};Layers{50};Recombine;
};


Physical Volume(99)={out[1]};
Physical Surface(98)={out[0]};