An amplifier A has $6 \; d \mathrm{B}$ gain and $50 \; \Omega$ input and output impedances. The noise figure of this amplifier as shown in the figure is $(a)$ is $3 \; d \mathrm{B}$. A cascade of two such amplifiers as in the figure is will have a noise figure of
- $6 \; d \mathrm{B}$
- $8 \; d \mathrm{B}$
- $12 \;d \mathrm{B}$
- None of the above