Figure P18-39 shows two similar unit pulse waveforms. The only difference is that the first pulse is positive from \(-T / 2\) to \(T / 2\), while the second pulse goes from \(+\mathrm{A}\) to \(-\mathrm{A}\) at \(t=0\). Find the Fourier transforms of each signal and plot their respective frequency responses. Explain the null at \(\omega=0\) in the second response.