Q4) For each subcarrier to experience flat fading and therefore avoid the ISI, we need OFDM symbol time T> Tm = 3 us. In this case, Find the needed number of subscribers N given that the available Bandwidth B=10MHz and L=0. Note T=NTs+LTS L= length of Cyclic prefix 1/Tm=Bc = coherence bandwidth over witch the channel has constant or stationary effect