原书上的代码：
$Title The Transportation Problem of Linear Programming

Sets
    i canning plants /Seattle,SanDiego/
    j markets /NewYork,Chicago,Detroit/;

Parameters
    a(i) capacity of plant i in cases
         /Seattle 350
         SanDiego 600/
    b(j) demand at market j in cases
         /NewYork 325
          Chicago 300
          Detroit 275/;
Table d(i,j) distance in thousands of miles
                     NewYork    Chicago    Detroit
          Seattle     2.5          1.7        1.8
          SanDiego    2.5          1.8        1.4

Scalar f in dollars per thousand miles /90/;

Parameter c(i,j) transpor cost in 1000s of dollars per cases;
          c(i,j) = f*d(i,j)/1000;

Variables
         x(i,j) shipment quantities in cases
         z total transportation costs in 1000s of dollars;

Positive Variable x;

Equation
         cost define objective function
         supply(i) observe supply limit at plant i
         demand(j) satisly demand at market j;
cost.. z =e= sum((i,j),c(i,j)*x(i,j));
supply(i)..   sum(j,x(i,j)) =l= a(i);
demand(j)..  sum(i,x(i,j)) =g= b(j);

Model transport /all/;
solve transport using lp minimizing z;
display x.l,x.m;

谢谢啦！！我最后一个求和公式里面错了。