which information, this is the complete problem

Let G = (V. E) be an undirected, acyclic, connected graph (that is, a tree). For any vertex V EV, the eccentricity of v is the length of a longest path from v to any other vertex of G. A vertex of G with minimum eccentricity is called an omphalos of G. 1. Design an efficient algorithm that computes an omphalos of G. (O(n + m)-time is possible and that should be your goal.) Provide some arguments behind the correctness of your algorithm and give the analysis of its asymptotic (worst-case) running time. 2. Is the omphalos unique? If not, how many different omphaloi can a tree have