Fading margin can be defined as the incremental E_b / N₀, in decibels, required to provide a certain desired error probability in a fading channel as could be achieved with the same modulation technique in a nonfading channel. Assume that a bit error probability of 10^-4 is specified.
Find the fading margin required for the following cases:

(a) BPSK; 

(b) DPSK; 

(c) Coherent FSK; 

(d) Non-coherent FSK.