Calculate the RMS delay spread for an HF radio channel for which: P(T) = 0.68(T) + 0.38(T-0.2) + 0.18(T-0.4) where t is measured in milliseconds. Determine whether a 5 KHz signal would experience flat fading or frequency selective fading. P(x) 0.6 0.3 0.1 0 0.2 0.4 T (msec)