I'm trying to model a situation where demand is a function of the supply of medical equipments. The equipment costs are already covered, hence price is not taken into consideration. The supply however should be less than the storage. All of the models that are currently over the internet are based on demand and supply equations which are price dependent. Can someone help me formulate an equation in which demand is dependent on the supply and supply is dependent on the demand. However, the supply must be less than the storage of a hospital.