Answer question 25) ~ 27) based on the problem description below. Consider the problem setting of 21) ~ 24) (Luckman Shipping Co.). After an internal meeting, the following changes are made compared to the situation in part A). First, the firm decides that both requirements ((i) and (ii)) are waived due to rearrangement of the shipping routes. Second, in addition to the existing van (indexed by 1) there are three other vans (indexed by 2,3,4) are available. Now, all four vans can be used, with each subject to a cost if the van is used. The information on the four vans are summarized below. Van Capacity (pound) Cost (in $1000) 2000 500 2 1000 400 3 750 300 4 500 200 The firm needs to decide on a loading plan (in other words, which item to be shipped by which van). Note that it is not necessary that all items are shipped. The goal of the firm is to maximizethe total value shipped net of total costs. To solve this problem, the manager decides to set up another MIP and he redefines the following decision variables: X, = 1 if item j is loaded on van i, otherwise X, = 0. { = 1, .".,4 and / = 1,.". ,5. Call Xi's "X variables". S, = 1 if item j is shipped, otherwise $, = 0. / = 1, ... ,5. Call S,'s "S variables". U. = 1 if van i is used, otherwise U, = 0. { = 1, ".",4. Call U,'s "U variables".25) (4 points) The objective of this MIP is: 26) (4 points) To express the capacity limit of van 2, the constraint is: 27) (4 points) For item 3, we need a constraint to establish the linkage among the relevant X variables, S variables and U variables (whichever variables are relevant to this item). This constraint is