Wireless Technology Dec-2015 Solved Numerical

Consider a single high-power transmitter that can support 100 voice channels covering a given service area. Let the service are be divided into seven smaller area cells. As shown in figure, each supported by lower power transmitters. The available spectrum of 100 voice channels is divided into 4 groups of 25 channels each.The cells (1,7)(2,4),(3,5) and 6 are assigned distinct channel  groups. Show that the total number of channels that can be supported is enhanced to 175 to cover the same service area.