3-15. Consider the following channel scattering function obtained by sending a 900-MHz sinusoidal input into the channel: S(T, p) = { () p = 70 Hz, 28(-.022 us) p = 49.5 Hz, 0 else, where 1 and 2 are determined by path loss, shadowing, and multipath fading. Clearly this scattering function corresponds to a two-ray model. Assume the transmitter and receiver used to send and receive the sinusoid are located 8 m above the ground. (a) Find the distance and velocity between the transmitter and receiver. (b) For the distance computed in part (a), is the path loss as a function of distance pro- portional to d2 or d4? Hint: Use the fact that the channel is based on a two-ray model. (c) Does a 30-kHz voice signal transmitted over this channel experience flat or rather frequency-selective fading?