帮我看看这段lingo代码，我不明白为什么一直出现error code11的错误

MODEL:
SETS:
QUARTERS/1,2,3,4/:DEM,RP,OP,INV;
ENDSETS

MIN=@sum{QUARTERS:400*RP(i)+450*OP+20*INV};
@FOR{QUARTERS{I}:RP{I}<40};
@FOR{QUARTERS{I}|I#GT#1:
INV{I}=INV{I-1}+RP{I}+OP{I}-DEM{I};};
INV{1}=10+RP{1}+OP{1}-DEM{1};
DATA:
DEM=40,60,75,25;
ENDDATA
END

是圆括号()不是花括号{}
MODEL:
SETS:
QUARTERS/1,2,3,4/:DEM,RP,OP,INV;
ENDSETS
MIN=@sum(QUARTERS:400*RP+450*OP+20*INV);
@FOR(QUARTERS(I):RP(I)<40);
@FOR(QUARTERS(I)|I#GT#1:
INV(I)=INV(I-1)+RP(I)+OP(I)-DEM(I));
INV(1)=10+RP(1)+OP(1)-DEM(1);
DATA:
DEM=40,60,75,25;
ENDDATA
END

没有问题，可以运行出来，运行结果 ： linearization components added: constraints: 20 variables: 5 global optimal solution found. objective value: 29.83636 objective bound: 29.83636 infeasibilities: 0.000000 extended solver steps: 0 total solver iterations: 17 model class: milp total variables: 15 nonlinear variables: 0 integer variables: 5 total constraints: 25 nonlinear constraints: 0 total nonzeros: 73 nonlinear nonzeros: 0 variable value reduced cost x1 218.1818 0.000000 y1 1.000000 4300.000 x2 0.000000 0.5718182e-01 y2 0.000000 -2700.000 x3 736.3636 0.000000 y3 1.000000 2500.000 x4 0.000000 0.2263636e-01 y4 0.000000 -2200.000 x5 45.45455 0.000000 y5 1.000000 4500.000 row slack or surplus dual price 1 29.83636 1.000000 2 336.3636 0.000000 3 0.000000 0.2983636e-01 4 0.000000 0.6181818e-03 5 0.000000 0.2363636e-02