The LINGO code The calculation results model: sets: P/P1..P4/:price;! Construction cost; T/T1..T4/:time;! Engineering capacity to meet the demand for water supply; C/C1..C4/:capacity;! Engineering capacity; links(P,T):x; endsets min=@sum(P(i):price(i)*x(i,1))+ @sum(P(i):price(i)*x(i,2))*(1+0.10)^(-@sum(T(i):time(i)*x(i,1)))+ @sum(P(i):price(i)*x(i,3))*(1+0.10)^(-@sum(T(i):time(i)*(x(i,1)+x(i,2))))+ @sum(P(i):price(i)*x(i,4))*(1+0.10)^(-@sum(T(i):time(i)*(x(i,1)+x(i,2)+x(i,3))));!Objective function; @sum(T(i):time(i)*(x(i,1)+x(i,2)))>=10;! Constraints of water supply demand time; @sum(C(i):capacity(i)*(x(i,1)+x(i,2)))>=5;! Constraints of engineering capacity increases water supply; @for(P(j):@sum(C(i):x(i,j))=1); @for(P(i):@sum(C(j):x(i,j))=1); @sum(P(j):@sum(C(i):x(i,j)))=4;! Constraints of project construction; @for(P(j):@for(C(i):@bin(x(i,j))));!0-1 constraints; data: price=6400 10500 16000 4000; time=2.68 11.58 8.42 2.11; capacity=1.28 5.50 4.00 1.00; enddata end Local optimal solution found. Objective value: 16923.85 Objective bound: 16923.85 Infeasibilities: 0.000000 Extended solver steps: 11 Total solver iterations: 448 Elapsed runtime seconds: 0.10 Model Class: PINLP Total variables: 16 Nonlinear variables: 16 Integer variables: 16 Total constraints: 12 Nonlinear constraints: 1 Total nonzeros: 80 Nonlinear nonzeros: 16 Variable Value Reduced Cost PRICE(P1) 6400.000 0.000000 PRICE(P2) 10500.00 0.000000 PRICE(P3) 16000.00 0.000000 PRICE(P4) 4000.000 0.000000 TIME(T1) 2.680000 0.000000 TIME(T2) 11.58000 0.000000 TIME(T3) 8.420000 0.000000 TIME(T4) 2.110000 0.000000 CAPACITY(C1) 1.280000 0.000000 CAPACITY(C2) 5.500000 0.000000 CAPACITY(C3) 4.000000 0.000000 CAPACITY(C4) 1.000000 0.000000 X(P1, T1) 0.000000 0.000000 X(P1, T2) 0.000000 1224.752 X(P1, T3) 1.000000 0.000000 X(P1, T4) 0.000000 0.000000 X(P2, T1) 1.000000 390.2178 X(P2, T2) 0.000000 0.000000 X(P2, T3) 0.000000 0.000000 X(P2, T4) 0.000000 2600.677 X(P3, T1) 0.000000 5320.812 X(P3, T2) 0.000000 855.1000 X(P3, T3) 0.000000 0.000000 X(P3, T4) 1.000000 1252.020 X(P4, T1) 0.000000 0.000000 X(P4, T2) 1.000000 2756.736 X(P4, T3) 0.000000 1582.681 X(P4, T4) 0.000000 1546.801