Cut and Glue

Geometry Level 2

What is the external surface area of this staircase (including the bottom) if it was constructed from four pieces of a cubic foot of wood?

Details: The height of part A is $\frac{1}{3} \text{ ft}$ and the heights of parts B and C are $\frac{1}{4} \text{ ft}$ each.

12\hspace{2mm} \text{ ft}^2

11\hspace{2mm} \text{ ft}^2

10 \frac{2}{3} \hspace{2mm} \text{ ft}^2

10 \frac{1}{3}\hspace{2mm} \text{ ft}^2

8 \frac{1}{3}\hspace{2mm} \text{ ft}^2