Design a five-element binomial array with elements placed along the z-axis. (a) Derive the excitation coefficients. (b) Write a simplified expression for the array factor. (c) For a spacing of d = 31/4, determine all the angles theta (in degrees) where the array factor possesses nulls. (d) For a spacing of d = 31/4, determine all the angles theta (in degrees) where the array factor possesses main maxima.