2. The available wavelength band for silicon based fiber consists of O-band(1260 to 1360 nm), E-band (1360 to 1460 nm), S-band (1460 to 1530), C-band (1530 to 1565 nm), L-band (1565 to 1625 nm), and U-band (1625 to 1675 nm), respectively. Assumed all the above wavelength bands are all used to support CWDM system. How many channels can be obtained