lingo新手求教，求找错

moonway

如题，我下载的lingo破解版不能指出具体错误，请大家帮忙了···
MODEL:
TITLE production of boat
sets:
     demand/1..4/:season;
     cost/1..3/:b;
     produce/1..4/:normal,extra,left;
endsets

data:
season=40 60 75 25;
b=20 400 450;
enddata


min=@sum((produce(i),cost(i)):c(i)*b(i));
@for((produce(i),demand(i))|i#GT#1:normal(i)+extra(i)+left(i-1)-left(i)=season(i));
@for(produce(i):normal(i)<40);
season(1)=10+normal(1)+extra(1)-left(1);
END