Answer: 2.68cm²
Explanation:
The front face has surface area 4x11 = 44mm². The one facing the left has surface area 6x4 = 24mm². Finally, the one facing upwards has surface area 11x6 = 66mm². Adding these up, we get 134mm² for the three faces we can see. Double this for the ones which are hidden and we get 268mm², or 2.68cm².