代码如下，请问怎么修改呀
model:
sets:
s/1..1500/:i;
t/1..6/:j;
u(s,t):z;
endsets
max=20*y*@sum(s:@sum(t:z(i,j)));
y*n>0;
y*n<1200/11;
@for(s:@for(t:28<n*(z(i,j)+2)));
@for(s:@for(t:36>n*(z(i,j)+2)));
@for(s:@for(t:280>x*(z(i,j)+2)));
x>1/2;
x<19/2;
@for(s:@for(t:z(i,j)<10));
end