b$)$ Explain the main scattering processes that contribute to the radar cross$-$section $(RCS)$ of an airframe.

c$)$ Describe the elements of Global Navigation Satellite Systems $($GNSS$),$ e$.$g$.$ the Global Positioning System $($GPS$),$ and briefly explain how receivers locate themselves.

d$)$ An electro$-$optic system has a field of view of $6060$ and has a $20482048$ focal plane array. Find the range at which the critical dimension of $25$ metres of an aircraft covers $100$ pixels. $($Ans: $500$ m $)$