现需要将城市s的石油通过管道运送到城市t，中间有4个中转站v1、v2、v3和v4，城市与中转站的连接以及管道的容量如图所示，求从城市s到t的最大流。
需要用lingo解决
不胜感激


model:
sets:
point/vs,v1,v2,v3,v4,vt/;
route(point,point)/vs v1,vs v2,v1 v2,v1 v3,v2 v4,v3 v2,v3 vt,v4 v3,v4 vt/:transport,capacity;
endsets
data:
capacity=8 7 5 9 9 2 5 6 10;
enddata
max=z;
z=@sum(point(j)|@in(route,@index(point,vs),j):transport(1,j));
@for(point(i)|i
#ne#
@index(point,vs)
#and#
i
#ne#
@index(point,vt):@sum(point(j)|@in(route,i,j):transport(i,j))=@sum(point(j)|@in(route,j,i):transport(j,i)));
@for(route:transport