P$4\mathrm{.}5-2.$ A baseband signal $m(t)$ is the periodic sawtooth signal shown in Fig. P$4\mathrm{.}5-2.$

a$)$ Sketch ${}_{FM}(t)$ and ${}_P(t)$ for this signal $m(t)$ if

${}_c=2{10}^6,k_1=2000$ and $k_p={}^{\text{'}2}$

b$)$ Show that the PM signal is a signal with constant frequency but periodic phase changes. Explain why it is necessary to use $k_p<mi></mi>$ in this case for reception purposes. $[$Note that the PM signal has a constant frequency but has phase discontinuities corresponding to the discontinuities of $m(t).1$