Consider a real-valued base-band signal $x(t)$, band limited to $\text{10 kHz}$. The Nyquist rate for the signal $y\left ( t \right )=x\left ( t \right )x\left ( 1+\dfrac{t}{2} \right )$ is
- $\text{15 kHz}$
- $\text{30 kHz}$
- $\text{60 kHz}$
- $\text{20 kHz}$