I ROUNDUP  
b Virginia's four largest phone companies will roll back their rates by about $37 million on Jan. 1, resulting in lower bills for most of the stateÛªs 2.8 million telephone customers, the State Corporation Commission says.</br></br>Actual savings will vary. For example* the decrease will amount to 50 cents a month for customers of the largest phone company in the state, Chesapeake and Potomac Telephone Co. of Virginia, said William Irby, manager of rates and costs for the SCCÛªs Communications Division.</br></br>The rate decreases should also bring reductions among other corporations supplying telephone service, he said. American Telephone & Telegraph Co., the largest long-distance phone company, has already said it will reduce rates next month.</br></br>Federal tax reform, which lowered corporate tax rates, prompted the SCC to order the state's five largest telephone firms to reduce their rates. The fifth of the major firms, General Telephone Co. of the Southeast, is appealing the commissionÛªs order.</br></br>The Treasury Department auctioned $6,403 billion worth of 13-week bills at an average discount of 5.73 percent, down from 5.96 percent last week. The government also sold $6,401 billion of 26-week bills at an average discount of 6.32 percent, down from 6.48 percent last week.