Consider a sampled signal $y(t)=5 \times 10^{\circ}$ ${ }^6 x(t) \sum_{(n-\infty}^{+\infty} \delta \left(t-n \mathrm{T}_x\right)$ where $x(t)=10 \cos \left(8 \pi \times 10^3\right) t$ and $T_s=100 \; \mu \mathrm{sec}$. When $y(t)$ is passed through an ideal lowpass filter with a cut-off frequency of 5 $\mathrm{kHz}$, the output of the filter is
- $5 \times 10^{-6} \cos \left(8 \pi \times 10^3\right) t$
- $5 \times 10^{-5} \cos \left(8 \pi \times 10^3\right) t$
- $5 \times 10^{-1} \cos \left(8 \pi \times 10^3\right) t$
- $10 \cos \left(8 \pi \times 10^3\right) t$