A box of dimension $$40\times35\times28\text{ units}$$ is used to keep smaller cuboidal boxes so that no space is left between the boxes. If the box is packed with $$100$$ such smaller boxes of the same size, then dimension of the smaller box is

A

$$7\times8\times7$$

B

$$8\times7\times7$$

C

$$7\times7\times8$$

D

$$20\times7\times7$$