Henrietta Inc., manufactures hammers in $3$ locations, Denver, Chicago and Dallas. Completed hammers are shipped to two distribution centers in Wichita and St Louis. The distribution centers then ship to the final destinations of Boston & New York. Supply$/$demand & shipping cost information is below.

From$/$To Wichita St Louis Boston New York Supply

Denver $$20$ $$19400$

Chicago $$22$ $$25400$

Dallas $$18$ $$17400$

Wichita $$11$ $$12$

St Louis $$9$ $$12$

Demand $600600$

Using Xij where i $=$ source and j $=$ destination, which equation indicates the Chicago supply constraint?