A CW radar uses linear frequency modulation to determine both range and range rate. The radar wavelength is \(\lambda=3 \mathrm{~cm}\), and the frequency sweep is \(\Delta f=200 \mathrm{kHz}\). Let \(t_{0}=20 \mathrm{~ms}\). (a) Calculate the mean Doppler shift. (b) Compute \(f_{b u}\) and \(f_{b d}\) corresponding to a target at range \(R=350 \mathrm{~km}\), which is approaching the radar with radial velocity of \(250 \mathrm{~m} / \mathrm{s}\).