Let p be an odd primer number and N=2^(p)1. The goal of this problem is to show
 that 2^(N-1) is equivalent to 1 mod N, namely that N passes the Fermat primality
 test for a=2. [Note: This doesn't mean that N is necessarily prime. For example,
 if p=11, N=2047=23*89 and if p=23, then N=8388607=47*178481.] Then, do the following:

 a) Explain why 2^p is equivalent to 1 mod M is true

 b) Show that N-1 is equivalent to 0 mod p

 c) Use parts a and b to show that 2^(N-1) is equivalent to 1 mod N