A $200 \mathrm{V}$ bulb takes a current of $0.2 \mathrm{A}$. The length of its filament is $22 \mathrm{cm}$ and the specific resistance of the material of the filament is $7 \times {10}^{-5} \mathrm{\Omega }-\mathrm{cm}$. Find the radius of the filament $(\pi = \frac{22}{7})$.

A rectangular block of iron has dimensions $1.2 \mathrm{cm} \times 1.2 \mathrm{cm} \times 15 \mathrm{cm}$. Compute the resistance of the block between the two square ends. The specific resistance of iron at room temperature is $9.68 \times {10}^{-8 }\mathrm{\Omega } \mathrm{m}$.