# Overview

The TRANS procedure is used to solve the
*transportation problem*, which is a type of *network flow problem*.
A node of a transportation problem is either a *source node*
or a *destination node*.
Each source node is able to supply a specified number of *flow
units*; each destination node has a *demand* for a specified number of
flow units. Each *arc* of a transportation problem originates at a
source node
and terminates at a destination node.
Some arcs can have *capacities* (the maximum amount of flow that they
can convey) and *lower flow bounds* (the minimum amount of flow that the
arc can convey). Arcs also have per unit traversal costs,
simply referred to as *costs*
(for example, the cost incurred when one unit of
flow is conveyed through an arc).

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