I need help with this problem

you run a small company providing napkins for hotels. For

each of the next 5 days you know how many napkins you’ll

need: 80, 70, 120, 150, 100, respectively. Each morning

when delivering your napkins, you can pick up the used

ones (what you delivered previous day). If you send those

(or some of those) for a cleaning (for $a/napkin) than they

can be used as new ones at the next morning delivery. You

can also buy new napkins at $b/napkin any given day,

before you make the deliveries for that day. You can also

keep clean (new) napkins in your stock for $c/day/napkin

for following days. Initially you have 100 napkins in stock.

Create a model to find a cost minimal plan (of

buying/cleaning/storing) to fulfill your contract (for the

next 5 days) create a .dat and .mod file

**Here is my dat file**

**data**

param n := 5;

**param** demand :=

1 80

2 70

3 120

4 150

5 100;

**param** cost_cleaning := 0.50; # Set the actual cleaning cost here

**param** cost_new := 0.75; # Set the actual cost of buying new napkins here

**param** cost_stock := 0.10; # Set the actual cost of storing napkins here

here is my mod file

**param** n; # Number of days

**set** Days := 5;

**param** demand{Days};

**param** cost_cleaning;

**param** cost_new;

**param** cost_stock;

**param** initial_stock := 100; # Initial stock of napkins

**var** x{Days} >= 0; # Number of napkins bought on each day

**var** y{Days} >= 0; # Number of napkins cleaned on each day

**var** s{Days} >= 0; # Number of napkins kept in stock after each day

# Objective function: Minimize the total cost

**minimize** TotalCost:

cost_new * **sum** {d **in** Days} x[d] +

cost_cleaning * **sum** {d **in** Days} y[d] +

cost_stock * **sum** {d **in** Days} s[d];

**subject** **to** DemandConstraint {d **in** Days}:

s[d] + initial_stock + x[d] = demand[d] + y[d];

# The number of napkins in stock cannot be negative

**s.t.** NonNegativeStock {d **in** Days}:

s[d] >= 0;

# Variables representing buying and cleaning cannot be negative

**s.t.** NonNegativeBuys {d **in** Days}:

x[d] >= 0;

**s.t.** NonNegativeCleaning {d **in** Days}:

y[d] >= 0;

# Solve the LP model

**data** SAHC-hw4.dat;

**option** solver cplex;

**solve**;

**display** x;

**display** y;

**display** s;

**display** TotalCost;

i keep getting this error

n is already defined

context: param >>> n; <<< # Number of days

ampl:

please help me ASAP