There are conditions that limit the investment alternatives: - At least two of projects 1,3,5, and 6 must be undertaken. - If either project 3 or 5 is undertaken, they must both be undertaken. - Project 4 cannot be undertaken unless both projects 1 and 3 also are undertaken. The budget for this investment period is $220 million. objective function in millions of dollars.) Max18x1+8x2+16x3+17x4+23x5+12x6 s.t. constraint on projects 1,3,5, and 6 constraint on projects 3 and 5 constraint on projects 1 and 4 constraint on projects 3 and 4 budget constraint (b) Solve the model formulated in part (a). What is the optimal net present value (in millions of dollars)? $ million How much of the budget is unused (in millions of dollars)? $ million