# Exchange

The exchange module sets up market contracts for the sale and purchase of power.

## Momentary contracts

Momentary contracts are set up by creating a market step in the logical model. See [market step documentation](lmmarketstep) for more details. The dynamic response type will change the way the step cost and capacity behaves during the simulation.

## Price elastic contracts

Price elastic contracts are set up the same way. The dynamic response type will change the way the step cost and capacity behaves during the simulation, where price at the end of a decision problem will influence the capacity of the steps in the next problem. See [market step documentation](lmmarketstep) for more details about price elasticity.

## Dump load and rationing

The module will set up slack variables in the form of dump loa and rationing. The size and cost of these variables is user configurable, see [module input](moduleexchange). These variables are necessary to ensure problem feasability.