If the half value layer for iron is \(1.7 \mathrm{~cm}\) for \(1.332 \mathrm{MeV}\) photons and the exposure rate from a source is \(1000 \mathrm{mR} / \mathrm{h}\), calculate

(a) \(\mu\left(\mathrm{cm}^{-1}ight)\),

(b) the thickness of iron required to reduce the exposure rate to \(100 \mathrm{mR} / \mathrm{h}\), and to \(1 \mathrm{mR} / \mathrm{h}\).