Which of the following is NOT categorized under types of cooperative purchasing systems?

The option of public auctions is not categorized under types of cooperative purchasing systems because cooperative purchasing involves collaboration among multiple entities to obtain goods or services collectively, aiming for better pricing and terms. Cooperative purchasing systems, such as a joint purchasing system, cooperative pricing, and state contracts, are organized approaches where entities like municipalities or government agencies come together to leverage their purchasing power.

In this context, public auctions are typically a process used for selling items to the highest bidder. This method does not embody the cooperative aspect of joint purchasing or shared resource management. Instead, it operates on individual bidding rather than collective procurement, which is the defining feature of cooperative purchasing systems. Consequently, this makes public auctions distinct from the other options, which involve formal agreements and partnerships between various organizations to secure favorable contracts.