lingo 报错 model is ill defined

题目

lingo 报错 model is ill defined
model:
sets:
set1/1..4/:per,low,E,x,q,cost;
endsets
data:
per=1,2,4.5,6.5;
low=103,198,52,40;
q=2.5,1.5,5.5,2.6;
E=28,21,23,25;
M=?;
cost=0;
risk=?;
enddata
max=@sum(set1(i):x(i))+@sum(set1(i):cost(i));
@sum(set1(i)|i:x(i))=M;
cost(i)=@if(x(i)#gt#low(i),x(i)*per(i),low(i)*per(i));
@max(set1(j):(x(j)/M*q(j)))

答案

说明语法是没有问题的,检查逻辑错误.