The volume of the material in the cracker is
(volume of the outer cylinder) minus (volume of the cylindrical hole)
The volume of any cylinder is
V = (π) (radius)² (length)
For the outer cylinder:
V = (π) (8 mm)² (18 mm)
For the cylindrical hole:
V = (π) (4 mm)² (18 mm)
The solid material in the whole cracker:
V = (π) (8 mm)² (18 mm) - (π) (4 mm)² (18 mm)
V = (π) (18mm) {(8 mm)² - (4 mm)²}
V = (18π mm) (48 mm²)
V = (18π · 48) mm³
V = 2,714.3 mm³