Four identical cylindrical chalk-sticks, each of radius $r=0.5 \mathrm{~cm}$ and length $l=10 \mathrm{~cm}$, are bound tightly together using a duct tape as shown in the following figure.
The width of the duct tape is equal to the length of the chalk-stick. The area (in $\mathrm{cm}^{2}$ ) of the duct tape required to wrap the bundle of chalk-sticks once, is
- $20(4+\pi)$
- $20(8+\pi)$
- $10(8+\pi)$
- $10(4+\pi)$