Choose the correct answer of the following question:

We have,

Length of the rectangular sheet, $l=40 \mathrm{~cm}$,

Width of the rectangular sheet, $b=22 \mathrm{~cm}$ and

Height of the hollow cylinder, $h=40 \mathrm{~cm}$

Let the radius of the cylinder be $r$.

As, $l=h$

So, the circumference of base of the cylinder $=b$

$\Rightarrow 2 \pi r=22$

$\Rightarrow 2 \times \frac{22}{7} \times r=22$

$\Rightarrow r=\frac{22 \times 7}{2 \times 22}$

$\therefore r=3.5 \mathrm{~cm}$

Hence, the correct answer is option (a).