/**
* gets a valid transport firm that supports a package
*
* @precondition requires firms to be sorted by cost
* @param md
* @return
*/
public TransportFirm getTransportFirm(MailDelivery md) {
Priority p = md.priority;
double weight = md.weight;
double volume = md.volume;
for (TransportFirm t : firms) {
if (weight <= t.getMaxWeight()
&& volume <= t.getMaxVolume()
&& !(p.isAir() == !t.getType().isAir())) return t;
}
return null;
}
