A pyramid with a rectangular base is stacked on top of rectangular prism. The height of the composite figure is 10. The lengths of the rectangular base are 8 and 6 units. The height of the rectangular prism is 4.
Which expression represents the volume, in cubic units, of the composite figure?

One-third(8)(6)(6) + (8)(6)(4)
One-third(8)(6)(10) + (8)(6)(4)
(8)(6)(4) – (One-third)(8)(6)(6)
(8)(6)(4) – (One-third)(8)(6)(10)