1. For a given graph G-(V,E), a subset SSV is called an independent set if (u,v)EE for every pair of vertices u,vES. The three independent set problems ISD, ISO and ISF all have as input a graph G-(V,E). ISD also has as part of the input a natural number k. ISD is a decision problem: the question is whether or not there is a subset S of V with at least k elements such that (u,v)EE for every pair of vertices u,vES? ISO and ISF do not have yeso answers. The answer to ISO is an integer n - size of the largest independent set in graph G. The answer to ISF is subset S - largest independent set in graph G. Show that all three of these problems are polynomial-time Turing equivalent. L.e. show the solution of ISO and ISF that uses ISD as a subroutine. Also show a solution to ISD that uses ISO as a subroutine. Provide detailed pseudocode solutions with justification of correctness and running time