Debt Debt maturities (including sinking fund requirements) during the five years subsequent to December 31, 1999 were as follows: The weighted average interest rates for outstanding U.S. commercial paper at December 31, 1999 and 1998 were 6.60 percent and 5.96 percent, respectively. The weighted average interest rates for outstanding Canadian commercial paper at December 31, 1999 and 1998 were 5.17 percent and 5.30 percent, respectively. U.S. commercial paper is classified as long-term debt since it is backed by the long-term revolving credit facility discussed below.       The Company can borrow up to $720 million through an unsecured global revolving credit facility, which expires in May 2002. The global credit facility is primarily to be used to finance working capital and provide support for the issuance of commercial paper. At the Company's option, the interest rate on borrowings under the global credit facility is based on LIBOR, prime, federal funds or local equivalent rates. No compensating balances are required under the global credit facility; however, it does have an annual facility fee of 0.08 percent based on the Company's current credit rating. At December 31, 1999, foreign borrowings of $58 million were outstanding under the credit facility and the Company had $342 million available under this agreement.       The Company has issued unsecured medium-term notes under various shelf registration statements filed with the Securities and Exchange Commission. In 1998, the Company registered an additional $800 million for future debt issues. As of December 31, 1999, the Company had $487 million of debt securities available for issuance under the latest registration statement. The Company had unamortized original issue discounts of $18 million and $21 million for the medium-term notes and debentures at December 31, 1999 and 1998, respectively.       During the fourth quarter of 1999, the Company recorded an extraordinary loss of $4 million (net of income tax benefit of $3 million) in connection with the early retirement of $156 million of medium-term notes. The loss represents the payment of redemption premiums and the write-off of deferred finance costs.       At December 31, 1999 and 1998, the Company also had letters of credit outstanding totaling $134 million and $163 million, respectively, which primarily guarantee various insurance activities.       Interest paid for both continuing and discontinued operations totaled $206 million in 1999, $201 million in 1998 and $196 million in 1997.       The carrying amount of debt (excluding capital leases) was $2,341 million and $2,548 million as of December 31, 1999 and 1998, respectively. Based on dealer quotations that represent the discounted future cash flows through maturity or expiration using current rates, the fair value of this debt at December 31, 1999 and 1998 was estimated at $2,289 million and $2,623 million, respectively.       At December 31, 1997, the Company had outstanding an interest rate swap agreement effectively changing the interest rate exposure on $61 million of medium-term notes from variable to a 5.84 percent fixed rate. The swap matured in March 1998.