$onEmpty

Set i(*) supply /
'seattle', 
'san-diego' /;

Set j(*) markets /
'new-york', 
'chicago', 
'topeka' /;

Parameter d(i,j) distance in thousands of miles /
'seattle'.'new-york' 2.5, 
'seattle'.'chicago' 1.7, 
'seattle'.'topeka' 1.8, 
'san-diego'.'new-york' 2.5, 
'san-diego'.'chicago' 1.8, 
'san-diego'.'topeka' 1.4 /;

$offEmpty
