Erorr 149

cons8(j)… sum(i, z(i,j)) =e= d(j) * s(i);

why am i getting error 149 here

s(i) service level of state i
d(j) Demand of state j
z(i,j) number of humanitarian kits sent from state i to state j

What i should GAMS use for the s(i)? The control of i stops with the sum. The equation is controlled over j.

-Michael