An iron wire is $8.0\,\text{m}$ long and has a diameter of $0.50\,\text{mm}$. Its resistance is $R$. A second iron wire is $2.0\,\text{m}$ long and has a diameter of $1.0\,\text{mm}$. What is the resistance of the second wire?
- A$\frac{R}{16}$
- B$\frac{R}{8}$
- C$\frac{R}{2}$
- D$R$