lingo老是出现错误代码11,怎么解决

lingo老是出现错误代码11,怎么解决
MODEL:
title locate problem;
sets:
demand/1..6/:a,b,d;
supply/1..2/:x,y,e;
link(denand,supply):c;
endsets
data:
a=1.25,8.75,0.5,5.75,3,7.25;
b=1.25,0.75,4.75,5,6.5,7.25;
d=3,5,4,7,6,11;e=20,20;
enddata
init:
x,y=5,1,2,7;
endinit
[OBJ] min=@sum(link(i,j)):c(i,j)(((x(j)-a(i))^2+(y(j)-b(i))^2)/(1/2));
@for(demand(i):[DEAND_CON]@sum(supply(j):c(i,j))=d(i));
@for(supply(i):[SUPPLY_CON]@sum(demand(j):c(j,i))