Explanation : Suppose G = (v, E) and G1 = (v, E1) such that
E1 ≤ E and v1 ≤ v
Consider an example
Consider the w(e) = 1 of e ∉ E1
it means the cost
of v1
to v4
is only 1 other edges having cost 0. It is
noted that G1
is connected (As shown in example).