Hint: You can try using the following decision variables: P,- = # of tons of steel to produce in month i (i = 1,... ,4) l; = # of tons of inventory from month ito i+ 1 (i = 1,... ,4) (P0 = 2600, lo = 300) U,- = increase in production from month i- 1 to i (in tons) (i = 1,... ,4) D,- = decrease in production from month i - 1 to i(in tons) (i = 1,... ,4) Note: The production variables P,- are the main decision variables, because the inventory levels (and changes in the production levels) are determined once the production levels are set. Often the Pl's are called controllable decision variables and the lls (MS and Dis) are called denitional decision variables. In any event: Except for the \"min" in the objective function, don't formulate the problem with logic arguments, like \"it\