Consider a \(\mathrm{BF}_{3}\) neutron detector of length \(20 \mathrm{~cm}\). Find its efficiency for thermal \((0.025 \mathrm{eV})\) and fast \((1 \mathrm{MeV})\) neutrons. Assume the fill gas pressure to be

(a) \(0.5 \mathrm{~atm}\) and

(b) \(1 \mathrm{~atm}\).