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

Question

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

Answer 1

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