What is enterprise resource planning $($ERP$)?$

a$.$ connection of the plans, methods, and tools aimed at integrating separate enterprise system

b$.$ a means of managing all aspects of a customer's relationship with an organization to increase customer loyalty and retention and an organization's profitability

c$.$ the management of information flows between and among activities in a supply chain to maximize total supply chain effectiveness and corporate profitability

d$.$ integration of all departments and functions throughout an organization into a single IT system $($or integrated set of IT systems$)$ so employees can make decisions by viewing enterprise$-$wide information about all business operations