Optimality of A* (proof)
n Suppose some suboptimal goal G2 has been generated and is in the
fringe. Let n be an unexpanded node in the fringe such that n is on
a shortest path to an optimal goal G.
n f(G2)     > f(G)      from above
n h(n)     h^*(n)     since h is admissible
n g(n) + h(n)   g(n) + h*(n)
n f(n)      f(G)
Hence f(G2) > f(n), and A* will never select G2 for expansion