Answer
(a) $d = 5.0\times 10^{-3}~cm$
(b) The area has been magnified by a factor of 360,000
Work Step by Step
(a) The vessels are magnified by a factor of 600. We can find the diameter $d$ of the vessel:
$d = \frac{3.0~cm}{600}$
$d = 0.0050~cm$
$d = 5.0\times 10^{-3}~cm$
(b) Let the vessel's radius be $r$. We can find an expression for the area of the vessel:
$A = \pi~r^2$
In the micrograph, the radius is $600~r$. We can find the area of the image in the micrograph:
$A' = \pi~(600~r)(600~r)$
$A' = 360,000~\pi~r^2$
$A' = 360,000~A$
The area has been magnified by a factor of 360,000.