The volume of the part is the difference of the volume of the larger rectangular prism and the smaller rectangular prism so we have:

Vpart=Vlarger−Vsmaller

The volume of a retangular prism is V=lwh. For the larger prism, l=8 cm, w=4 cm, and h=5 cm. For the smaller prism, l=4 cm, w=1 cm, and h=5 cm. So,

Vpart=(8)(4)(5)−(4)(1)(5)

Vpart=160−20

Vpart=140 cm^3

So, the correct answer is choice B.

Leo chose D because instead of subtracting, he added the volume of the prisms which is incorrect.

Vpart=Vlarger−Vsmaller

The volume of a retangular prism is V=lwh. For the larger prism, l=8 cm, w=4 cm, and h=5 cm. For the smaller prism, l=4 cm, w=1 cm, and h=5 cm. So,

Vpart=(8)(4)(5)−(4)(1)(5)

Vpart=160−20

Vpart=140 cm^3

So, the correct answer is choice B.

Leo chose D because instead of subtracting, he added the volume of the prisms which is incorrect.