题目内容：

lingo求矩阵列之和
怎么求在J=1的时候所有volume(I,J)的和啊
sets:
supplyment/s1..s20/:supply;
receiver/r1..r20/:demand;
links(supplyment ,receiver):cost,volume;
endsets
目标函数;
min=@sum(links:cost*volume);
需求约束;
@for(receiver(J):
@sum(supplyment(I):volume(I,J))=demand(J));
产量约束;
@for(supplyment(I):
@sum(receiver(J):volume(I,J))=supply(I));