A scanning electron micrograph of xylem vessels in a corn root shows the vessels magnified by a

Question:

A scanning electron micrograph of xylem vessels in a corn root shows the vessels magnified by a factor of 600. In the micrograph the xylem vessel is 3.0 cm in diameter.
(a) What is the diameter of the vessel itself?
(b) By what factor has the cross-sectional area of the vessel been increased in the micrograph?