To find the volume of this triangular prism:
⇒ must use the formula:

Let's consider the information given:
- Volume: 108 in³
- Height: 9 in
Let's plug this into the equation:

Now let's consider the area of the base formula

By plugging all these choices into the Area of Base's formula,
⇒ only the second choice or 4in by 6in works

Answer: Second choice or 4in. by 6in.
Hope that helps!