The following constraint insures that node A is the source node: XAB+XBC+XBD=0XABXBCXBD=05XAB2XBC2XBD=030XAB10XBC40XBD=0 We do not need to add a constraint for this source node. Question 3 (1 point) When we model the problem as a maximum-flow problem, which of the following is correct? One feasible (not necessary optimal) solution is XAB=30,XAC=20,XBC=10,XBD=20, XCD=30 One feasible (not necessary optimal) solution is XAB=1,XAC=0,XBC=1,XBD=0,XCD=1 One feasible (not necessary optimal) solution is XAB=5,XAC=3,XBC=2,XBD=2,XCD=3 One feasible (not necessary optimal) solution is XAB=3,XAC=1,XBC=2,XBD=1,XCD=1 One feasible (not necessary optimal) solution is XAB=1,XAC=1,XBC=1,XBD=0,XCD=1 The objective function for the above problem is: MaxZ=XAB+XACMaxZ=5XAB+3XACMaxZ=XBD+XCDMaxZ=2XBD+3XCD Both options "a" and "c" are correct Question 5 (1 point) In a feasible solution to the maximum-flow problem above, suppose we know XAB=2, and XAC=3. What is the value of XBC, i.e., the flow in arc BC ? XBC=0 XBC is either 0 or 1 XBC=1 XBC is either 1 or 2 XBC=2 The following is a graph of a distribution network for shipping product from origin node A to destination node D. B and C are transshipment nodes. Arc capacity is shown in square brackets below each arc, and arc length (km) is shown above each arc - e.g., arc AB is 30km long, and has a capacity of 5 units/month. Let Xij represent the flow in arc ij (i.e., units/month shipped from node i to node j). We wish to determine the maximum number of units we can send from supply node A to demand node D, so we formulate the problem as a maximum-flow problem. Question 1 (1 point) The following constraint insures that node B is a transhipment node: XAB+XBC+XBD=0XABXBCXBD=05XAB2XBC2XBD=030XAB10XBC40XBD=0 We do not need to add a constraint for this transhipment node