Given that,
\(k=Boltzmann^\prime s constant=1.38\times{10}^{-23}\frac{Joules}{Kelvin}\)
\(T=Temperatureoftheconductor\in Kelvin=\left(27+273\right)=300K\)
\(B=Bandwidthofthenoisespectrum=\left(20-8\right)=12MHz\)
\(R=10K\mathrm{\Omega}\)
The r.m.s input noise power of the amplifier is
\(\sqrt{4kTBR}=\sqrt{4\times1.38\times{10}^{-23}\times300\times12\times{10}^6\times10\times{10}^3}=37.95µV\)