While the pervious discussion of public utility regulation seems fairly simple and straight forward, the actual determination of price (rates) for public utility services by regulatory commissions (often called the rate case) is very complex. For one thing, it is difficult to determine the value of the plant or fixed assets on which to allow a normal rate of return. Should it be the original cost of the investment or the replacement cost? More often than not, regulatory commissions decide on the former. Furthermore, since public utility companies supply the service to different classes of customers, each with different price elasticities of demand, many different schedules could be used to allow the public utility company to break evan. Evan more troublesome is the fact that a public utility company usually provides many services that are jointly produced, and so it is impossible to allocate costs in any rational way to the various services provided and customers served.