The table gives details about three different blood vessels, P, Q and R. One vessel is an artery, one is a capillary and one is a vein. From the table information, what is the cross-sectional area of the lumen of the vein? (Assume $\pi = 3.14$)
- A$12.6\,\text{mm}^2$
- B$19.6\,\text{mm}^2$
- C$50.2\,\text{mm}^2$
- D$78.5\,\text{mm}^2$