Question 1081941
Assuming the each hole is drilled through the opposing  36*23 cm^2 sides, their length each is 20 cm.


{{{2*36*23+2*23*20+2*36*20-4*pi(12/6)^2+2(2*pi*(12/2)*20)}}}
This setup is subtracting the surface which makes the holes on the opposising drilled sides and adds the surface of each cylinder.