Let P be a prime ideal in R and let D=R-P denote the corresponding multiplicative submonoid. Prove that there exists a unique maximal ideal in D^{-1} R (that is generated by P in D^{-1} R ).
We know from Problem 218 that prime ideals of R not intersecting D are in one-to-one correspondence with the prime ideals of D^{-1} R. In particular the correspondence \phi is given by sending I to the ideal \phi(I) generated by I in D^{-1} R. It is obvious that \phi preserves the inclusion relation: I \subset J implies \phi(I) \subset \phi(J). Since the unique largest prime ideal not intersecting D is P, there is a unique maximal ideal in D^{-1} R.