) Develop an integer programming model for maximizing the net present value (in $ ). ( Let x1={1ifinvestmentalternative/isselected0otherwise for =1,2,3,4,5,6. Max4500x1+6500x2+11000x3+4500x4+7500x5+3500x6s.t.Year13000x1+2500x2+6000x3+2000x4+5000x5+1000x610500Year21000x1+3500x2+4000x3+1500x4+1000x5+500x67000Year34000x1+3500x2+5000x3+1800x4+4000x5+900x68750 (b) Assume that only one of the warehouse expansion projects can be implemented. Modify your model from part (a). In addition to the constraints from part (a), what additional constraint should be added to the integer programming model? x1+x21 Accordina to this model, what is the maximum net present value (in $ )? In addition to the constraints from part (a) and part (b), what additional constraint should be added to the integer programming model? x4x30 Accordinq to this model, what is the maximum net present value (in $ )? ) Develop an integer programming model for maximizing the net present value (in $ ). ( Let x1={1ifinvestmentalternative/isselected0otherwise for =1,2,3,4,5,6. Max4500x1+6500x2+11000x3+4500x4+7500x5+3500x6s.t.Year13000x1+2500x2+6000x3+2000x4+5000x5+1000x610500Year21000x1+3500x2+4000x3+1500x4+1000x5+500x67000Year34000x1+3500x2+5000x3+1800x4+4000x5+900x68750 (b) Assume that only one of the warehouse expansion projects can be implemented. Modify your model from part (a). In addition to the constraints from part (a), what additional constraint should be added to the integer programming model? x1+x21 Accordina to this model, what is the maximum net present value (in $ )? In addition to the constraints from part (a) and part (b), what additional constraint should be added to the integer programming model? x4x30 Accordinq to this model, what is the maximum net present value (in $ )