The correct answer is C. William J. Baumol.
William J. Baumol was an American economist who proposed a model to apply economic order quantity concept of inventory mangement to determine the optimum cash holding in a firm. The model, known as the Baumol model, is based on the assumption that a firm has a fixed amount of money that it must hold in cash at all times. The model then calculates the optimal amount of money that the firm should spend on inventory each period in order to minimize the costs of holding cash.
The Baumol model has been widely used by firms to manage their cash holdings. It is a simple and effective model that can help firms to reduce their costs of holding cash.
The other options are incorrect.
A. Keith V. Smith is an American economist who is known for his work on the economics of information. He is not known for his work on cash management.
B. Miller and Off are not economists. They are engineers who are known for their work on the design of manufacturing systems.
D. J. M. Keynes was a British economist who is known for his work on macroeconomics. He is not known for his work on cash management.