Assume that your network operates in a regulatory domain that allows use of the entire 5 GHz space allowed in the 802.11ac amendment. In your upcoming

802.11ac deployment, you would like to take advantage of the performance improvements that result from channel bonding. However, after extensive testing, you have determined that your mission-critical WLAN should not use channels requiring DFS support.

Given those two criteria (enable channel bonding and disable DFS channels), in the 5 GHz spectrum, how many non-overlapping 40 MHz channels will your system be able to use?