A retail chain store uses a centralized mainframe system that connects all of the cash registers within a region. Regional managers are able pull sales reports for all units on this mainframe, Salespeople are able to easily ring up and total customers purchases, as well as communicate with other associates at different machines. What is his mainframe system an example of$?$ More than one answer may be correct.

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mobile POS station

transaction processing system

cloud computing system

client$-$server network