To find the greatest, least, maximal and minimal elements for the relations in the given exercise.

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1. Let W, U, and S be graphs defined as follows: • V(W) is the set of countries in the world; • V(U) is the set of countries in the European Union; V(S) is the set of countries in the Schengen Area; ● for X = {W,U,S}, E(X) is the set of pairs of countries in V(X) that share a land border. Recall that land borders between countries in the Schengen Area are special in that they can be crossed without a passport. (a) The notions of a country and a land border are somewhat ambiguous. Explain the notions you will use to get a precise definition of the graphs W, U, and S. (b) Is S a subgraph of U? Is U an induced subgraph of W? Justify your answers. (c) Using non-mathematical language, explain what it means for a country x if VEV(S) and dw (v) = 0. Give all such countries. Let A = {v Є V(W) \V(S) such that |Nw(v)| > 0 and Nw (v) ≤ V(S)}. (d) Using non-mathematical language, explain what the set A represents in terms of countries and land borders. Give a specific element of A or explain why A…

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Chapter 8.5, Problem 26ES

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To find the greatest, least, maximal and minimal elements for the relations in the given exercise.

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1. Let W, U, and S be graphs defined as follows: • V(W) is the set of countries in the world; • V(U) is the set of countries in the European Union; V(S) is the set of countries in the Schengen Area; ● for X = {W,U,S}, E(X) is the set of pairs of countries in V(X) that share a land border. Recall that land borders between countries in the Schengen Area are special in that they can be crossed without a passport. (a) The notions of a country and a land border are somewhat ambiguous. Explain the notions you will use to get a precise definition of the graphs W, U, and S. (b) Is S a subgraph of U? Is U an induced subgraph of W? Justify your answers. (c) Using non-mathematical language, explain what it means for a country x if VEV(S) and dw (v) = 0. Give all such countries. Let A = {v Є V(W) \V(S) such that |Nw(v)| > 0 and Nw (v) ≤ V(S)}. (d) Using non-mathematical language, explain what the set A represents in terms of countries and land borders. Give a specific element of A or explain why A…

3. A spreadsheet consists of cells indexed by a row and a column. Each cell contains either a value or a formula that depends on the values of other cells. (a) Describe a graph, digraph, or network that models an arbitrary spreadsheet and allows you to answer the remaining parts of this question. (b) Explain, by referring to the graph, digraph, or network, when it is possible to change the value of cell x without changing the value of cell y. (c) Explain, by referring to the graph, digraph, or network, when it is possible to calculate the values of all cells in the spreadsheet. Consider the following spreadsheet with 5 rows, 7 columns, and 35 cells. For exam- ple, cell el contains a value, whereas cell al contains a formula that depends on the values cells el and 95. a b с d e f g 1 el+g5 al-c5 110 al+cl 180 f5-el c1+c2 2 al+bl a2+c4 240 a2+c2 120 f5-e2 e3+e5 3 a2+b2 a3-c3 100 a3+c1 200 f5-e3 f1+f2 4 a3+b3 a4+c2 220 a4+c2 100 f5-e4 f3+f4 5 a4+b4 a5-c1 130 a5+c5 120 g3+g4 gl+g2 (d) Can…

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