a$-$ A speech signal has a total duration of $20s.$ It is sampled at the rate of $8kHz$ and then encoded. The signal$-$to$-($quantization$)$ noise ratio is required to be $45dB.$ Calculate the minimum storage capacity $($size$)$ of a hard disk needed to accommodate $($store$)$ this digitized speech signal.

b$-$ Determine the Nyquist sampling rate and the Nyquist sampling interval for the following signal:

$m(t)=sin{c}^2(100t)+sin{c}^2(50t)+sinc(200t)$