$4.$ Consider an NRZ rectangular pulsed wave with a fundamental frequency of $10$ kHz and $(70\%)$ duty cycle. Consider the amplitude is $(+/-1)$

a$.(2$ points$)$ Write a mathematical equation that describes this wave as a convolution of the rectangle function and a comb function.

b$.(3$ points$)$ Calculate the FT of this RZ pulsed wave.

c$.(4$ points$)$ Calculate the values of the magnitude, of the FT$,$ at DC and first $6$ non$-$zero harmonics.

d$.(1$ points$)$ Obtain the Fourier Series equation of this RZ pulse wave in the harmonic domain.

e$.(3$ points$)$ Calculate the power of this wave using the calculated harmonics in part $4$c$)$