(a) Devolop an integer programming madel for maximizing the ret prosent walue (in $ ). (Let xj={1ifinvestmentabernative)issalected0otherwise Max s.t. Year 1 Year z Year 3 According to this model, what is the maximum net present value (in s)? 5 In addition to the constraints from part (a), what additional constraint should be added to the integer programming model? According 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? According to this model, what is the maximum net present value (in $ )