Answer:
[tex]\boxed{\sf a) \ 120 \ km^2}[/tex]
Step-by-step explanation:
The surface area is the total area of the faces added together.
Area of 2 triangles + Area of 3 rectangles
The two cross-sections are the triangles.
Area of triangle = base × height × 1/2
Area of a rectangle = length × width.
4 × 3 × 1/2 + 4 × 3 × 1/2 + 9 × 3 + 9 × 4 + 9 × 5
6 + 6 + 27 + 36 + 45
= 120
