lingo问题 错误代码29代码如下：model: !需求分配;sets: !定义集合;plant/p1..p8/: c

lingo问题 错误代码29
代码如下：
model: !需求分配;
sets: !定义集合;
plant/p1..p8/: capacity;
market/m1..m8/: demand;
links(plant, market): cost, volume;
endsets
min=@sum(links: cost*volume); !目标函数;
@for(market(J):
@sum(plant(I): volume(I,J))=demand(J)); !需求约束;
@for(plant(I):
@sum(market(J): volume(I,J))