Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Modelling and Differential Costs Evaluation of a Two Echelons Repair
  System through Infinite Servers Nodes Queuing Networks   After a short report of results on infinite servers queues systems, focusing
on its busy period, using networks of queues with infinite servers nodes a
model is constructed to study a two echelons repair system. These repair
systems may be useful, for instance, in the operation of a fleet of aircraft,
of shipping or of trucks. Additionally, it is shown how this model may be used
in the evaluation of differential costs.

4
The categories of this paper are: cond-mat
32
The categories of this paper are: atom-ph
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
26
The categories of this paper are: bayes-an
24
The categories of this paper are: dg-ga
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
3
The categories of this paper are: physics
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg