The Solution:
Given the figure below:
We are required to find the volume of the given prism.
By formula, the volume of a prism is:

In this case,
L=length=9 inch
W=width=5 inch
H=height=6 inch
The question says 3 cubes are removed from each corner.
The total cubes removed is:

So, the required volume is:

Therefore, the correct answer is [option A]