The volume of the smaller cube:
Volume of a cube = Length³
Volume of a cube = 1³ = 1 ft.³
The volume of the larger cuboid:
Volume of a cuboid = Length × Width × Height
Volume of a cuboid = 13 × 7 × 8
= 728 ft.³
The volume of the composed figure:
728 ft³ + 1 ft.³ = 729 ft³