(a) Give an expression for the ambiguity function for a pulse train consisting of 4 pulses, where the pulse width is \(\tau^{\prime}=1 \mu s\), and the pulse repetition interval is \(T=\) \(10 \mu \mathrm{s}\). Assume a wavelength of \(\lambda=1 \mathrm{~cm}\). 

(b) Sketch the ambiguity function contour.