KHALID ABDELAZIZ SUDAN’S central bank sharply devalued the currency yesterday, announcing a new regime to "unify" official and black-market exchange rates in an effort to overcome a crippling economic crisis and access debt relief. The change is a key reform demanded by foreign donors and the International Monetary Fund (IMF), but was delayed for months as shortages of basic goods and rapid inflation complicated a fragile political transition. The central bank set the indicative rate at 375 pounds to the dollar, several commercial banking sources said, from a previous official rate of 55 pounds. Recently, the dollar traded at between…