Question: A set of n cities is to be connected via communication links. The cost to construct a link between cities i and j is Cij , i ?= j . Enough links should be constructed so that for each pair of cities there is a path of links that connects them. As a result, only n - 1 links need be constructed. A minimal cost algorithm for solving this problem (known as the minimal spanning tree problem) first constructs the cheapest of all the 
width= links. Then, at each additional stage it chooses the cheapest link that connects a city without any links to one with links.
That is, if the first link is between cities 1 and 2, then the second link will either be between 1 and one of the links 3, . . . , n or between 2 and one of the links 3, . . . , n. Suppose that all of the width= costs Cij are independent exponential random variables with mean 1. Find the expected cost of the preceding algorithm if
(a) n = 3,
(b) n = 4.