DONALD E. GRAHAM will succeed his mother, Katherine Graham, as chief executive officer of The Washington Post Co. on May 9 and replace retiring Richard D. Simmons as its president . . . A SPY CAMERA concealed in a finger ring and used by the KGB has sold for $22,400, more than double its pre-sale estimate, auctioneers at Christie's in London said . . . A FIRE in a Chicago apartment building killed five people, including three children, authorities said Friday . . . A MILD EARTHQUAKE measuring 3.6 on the Richter scale shook central Virginia early Friday, rattling houses and awakening sleepers.