An investor is considering a total of I possible investment opportunities (i = 1, 2, ..., I), during a planning horizon covering T time periods (t = 1, 2, ..., T). A total of b_it dollars is required to initiate investment i in period t. Investment in project i at time period t provides an income stream a_i, t+1, a_i, t+2, .. ., a_i, T in succeeding time periods. This money is available for reinvestment in other projects. The total amount of money available to the investor at the beginning of the planning period is B dollars. Assume that the investor wants to maximize the net present value of the net stream of cash flows (c_t is the corresponding discount factor for period t). Formulate an integer-programming model to assist in the investor's decision. How should the model be modified to incorporate timing restrictions of the form