[AMPL 2574] " n undefined in : 350/delay[j,n]

Please help!

set CDN;

set OBJ;

set NTWK;

#Parameters for delay and bandwidth

param delay {CDN, NTWK} > 0;                                                  #parameters for network delay in serving an object from CDN j to a client in a network n

param bwidth {CDN,NTWK} > 0;                                                                #agreed upon bandwidth for the serving of an object from  CDN j to a client in network n

#Decision variables

var X{CDN,NTWK,OBJ} >=0;                                                         #the decision variable that indicate that whether a CDN serves a request or not, but in this case it relaxed

#Objectives#

minimize service_cost:

                                sum{i in OBJ, j in CDN, n in NTWK}unit_cost[j,i,n]*rate[j,i]*X[j,i,n];

#Constraints#

                subject to bdelay {j in CDN}: sum{i in OBJ, n in NTWK}rate[j,i]*size[i]* (bwidth[j,n]/delay[j,n])*X[j,i,n] >= 350/(delay[j,n]*sum{i in OBJ,n in NTWK}rate[j,i]);