4. We have seen that in OFDM-based wireless comm systems, a cyclic prefix is used to mitigate delay spread and its effects on the received signals. For the geometry shown below, calculate the delay spread at the receiver and state whether a 4.7 usec cyclic prefix would be sufficient to mitigate inter-symbol interference and clearly state why. You must show all of your work. Path 1 is a direct 5km path with a coherence bandwidth Bc1 = 950 kHz; Path 2 is a diffracted 5.4km path off of a lower level moving drone with a coherence bandwidth, Bc,2 = 225 kHz; Path 3 is a ground bounce of length 5.05km with a coherence bandwidth, Bc,3 = 300 kHz. You must show all of your work and it must be neat to receive credit. ((1)) Path 1 Path 2 Path 3