in march 2000 , the company entered into an $ 850 million revolving credit agreement with a syndicate of banks , which provides for a combination of either loans or letters of credit up to the maximum borrowing capacity . loans under the facility bear interest at either prime plus a spread of 0.50% ( 0.50 % ) or libor plus a spread of 2% ( 2 % ) . such spreads are subject to adjustment based on the company 2019s credit ratings and the term remaining to maturity