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Gas station model: The gas station model consists of a "create" modulesimulating the arrival of a car, a decision module to decide if the car will

pump gas depending on the availability of the pumps, an assign module todetermine the amount of gas and another assign module for calculation of theprofit. The box "report statistics" for variable "profit" was checked in orderto get a report of the profit. The station closes at 6 P but cars that arealready in the station are allowed to pump gas. !n the create module, anunlimited number of cars can be created by assigning a very large number #####$to the maximum number of arrivals. To account for not admitting cars after 6 Pin the model, an arrival cutoff entity is created at 6 P and the maximum numberof arrivals is changed from ##### to %.

!n order to check if a pump is available, a decision block is used. & car isallowed to enter the station if the number of busy pumps is less than '.(pecifically, the following condition is used: )Pumps.*!P + ' + ', wherePumps.*!P is an internal variable that is e-ual to the number of pumps used.This variable can be obtained using the expression builder as follows: asicProcess /ariables 01 Process 01 2umber in Progress.

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Car A rrives P umps Dispose of Car Buy Gas?T r u e

F a l s e

Car Leaves

D emand Calculate P rofit

CutoffCreate Arrival

A rrivalsA ss ign Max

ntityDispose of C utoff

!

!

!

!

!

!

! !

Discussion of results:'34 cars attempted to buy gas but %5 found an availablepump and purchased gas. The remaining 5# cars left without buying gas. Thislarge number means that lack of available pumps reduces substantially revenue

and profit. 7n the other hand, pump utili8ation is only 9.5. & costbenefitshould be performed to determine if more pumps should be installed.

The daily profit estimate is ;%9.

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;%4#.', which is very close to the profit estimated by simulation. >sing theavergae profit per car, we also found that if all of the remaining 5# cars hadpurchased gas, then there would be an additional profit of ;64.'.

ARENA Simulation Results

Pro?ect: (imulation of pump station @un execution date : 3

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G!(E@ATA0E=&2HA /&@!&BA(

!dentifier &verage =alf *idth inimum aximum Iinal /alueDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD

Profit /alue 6#.6'3 !nsuf$ .99999 %9.