Provided is a channel of 10 MHz bandwidth to be shared by 5 users. It is decided the channel is going to be shared by the users using FDM. A guard band of 1 MHz between each channel is allocated to avoid interference. Each user is given an equal share of bandwidth. Assume each user has 1 MB of data to transfer and can utilize the channel at full capacity.

Calculate the time required to transfer all data when:

a) The SNR of each channel is 10 dB.

b) The SNR of four channels is 10 dB and one channel is 5 dB.

Please provide suitable figures and description to explain your answer.