Task: Text Categorization
Input (English): Inventory control is modeled by the Markovian type of this concept, and in the Keynesian Cross, this equals the total output of an economy at efficiency. The Slutsky equation relates two forms of this. The Hicksian form of it assumes constant utility and is usually contrasted with the Marshallian form. Say's Law states that this is created by the presence of goods, and Keynes did work on the "aggregate" form of it. This quantity has a downward sloping curve and can be defined as the amount of a good or service consumers are willing to buy at a given price. For 10  points, identify this economic concept, commonly contrasted with supply.
Output (English): Science