Khối đa diện sau có bao nhiêu mặt?

Có 9 mặt: $\left(ABB\text{'}A\text{'}\right),\left(BB\text{'}C\text{'}C\right),\left(CC\text{'}D\text{'}D\right),\left(DD\text{'}A\text{'}A\right),\left(A\text{'}B\text{'}C\text{'}D\text{'}\right),$$\left(ABEF\right),$$\left(CDFE\right),\left(BEC\right),\left(ADE\right)$