The answer is actually D. Since 2.5 is a side of each tiny block, there is 3 sides that you are going to multiply together. There is 5,2 and 4 because we are multiplying the length,width and side. So the length is 2.5*5=12.5 which was correct. The width is 2.5*4=10 which you had but you crossed it out. Then lastly you are looking for the side of the shape. 2.5*2=5. Now that I have everything I just need to multiply everything together. 12.5*10*5=625 in³. I hope this helped you!