Answer
$d = 0.25~mm$
Work Step by Step
We can find the diameter $d$ of the hole:
$w = \frac{2.44~\lambda~L}{d}$
$d = \frac{2.44~\lambda~L}{w}$
$d = \frac{(2.44)~(633\times 10^{-9}~m)(4.0~m)}{2.5\times 10^{-2}~m}$
$d = 2.5\times 10^{-4}~m$
$d = 0.25~mm$
