A micrometer screw gauge is used to measure the diameter of a cylindrical metal rod. The diagram below gives an enlarged view of the micrometer screw gauge scale while the measurement is being taken. What is the cross-sectional area of the rod?
- A$3.81\,\text{mm}^2$
- B$11.4\,\text{mm}^2$
- C$22.8\,\text{mm}^2$
- D$45.6\,\text{mm}^2$