What? Trucks do have a bounded capacity. A truck cannot carry more than x kgs of packages or y liters of volume. Are you arguing against that?<p>If Amazon had asked for a single truck from UPS at 5 PM from warehouse A (the number of trucks ordered is a business decision), it can only allocate x kgs of packages or y liters of volume to that resource.<p>Edit: Just to clarify, the number of trucks may often be decided waaay in advance.