A pen stand made of wood is in the shape of a cuboid with four conical depressions to hold pens.

Radius of conical cavity = 0.5 cm and depth

(i.e., vertical height) = 1.4 cm

Volume of wood taken out to make one cavity

$=\frac{\mathbf{1}}{\mathbf{3}} \pi \mathbf{r}^{2} \times \mathbf{h}=\frac{\mathbf{1}}{\mathbf{3}} \times \frac{\mathbf{2 2}}{\mathbf{7}} \times(0.5)^{2} \times(1.4) \mathrm{cm}^{3}$

$=\frac{1}{3} \times \frac{22}{7} \times \frac{1}{4} \times \frac{14}{10} \mathrm{~cm}^{3}=\frac{11}{30} \mathrm{~cm}^{3}$

Volume of wood taken out to make four cavities

$=4 \times \frac{11}{30} \mathrm{~cm}^{3}=\frac{44}{30} \mathrm{~cm}^{3}$

volume of the wood in the pen stand

$=(15 \times 10 \times 3.5)-\frac{\mathbf{4 4}}{\mathbf{3 0}} \mathrm{cm}^{3}=(525-1.47) \mathrm{cm}^{3}$ (approx.) $=523.53 \mathrm{~cm}^{3}$ (approx.)