/**
* @see org.rioproject.costmodel.ResourceCostProducer#calculateResourceCost
*/
public ResourceCost calculateResourceCost(final double units, final long duration) {
if(costModel==null)
costModel = new ZeroCostModel();
double cost = costModel.getCostPerUnit(duration)*units;
return(new ResourceCost(getDescription(),
cost,
units,
costModel.getDescription(),