The cyclic prefix is intended to be long enough to mitigate the majority of expected multipath (e.g., in LTE CP durations are 4.7 usec). Since multipath comes from signals traveling longer distances than that of the shortest path signal, if the shortest path between Tx and Rx is 2.5km, what is the distance of the longest traveled multipath signal if the multipath delay should be significantly less than the CP duration (use factor of 3)? Signal propagation speed, c = 3.0 * 10^8 (m/s).