A baby born weighing less than a soda can and believed to be the smallest ever to survive went home Tuesday after nearly six months in the hospital. Rumaisa Rahman’s prognosis “is very good,” and she is expected to have normal physical and mental development, said Dr. Jonathan Muraskas, who provided care for the tiny girl and her larger twin sister, Hiba, after their births Sept. 19 at Loyola University Medical Center outside Chicago. Rumaisa weighed 8.6 ounces at birth and measured just 9 1/2 inches long. She is now 5 pounds, 8 ounces, and almost 17 inches long.