题目

A young man named Ted received a high-priced car from his brother as a Christmas present. On Christmas Eve when Ted came out of his office, a street urchin (顽童) was walking around the shining car. “Is this your car, Ted?” he asked. Ted answered, “Yes, my brother gave it for Christmas.” The boy was surprised. “You mean your brother gave it to you and it cost you nothing? Boy, I wish…” He hesitated(犹豫).Of course Ted knew what he was going to wish for. He wished he had a brother like that. But what the boy said surprised Ted greatly. “I wish,” the boy went on, “在△ABC中，三内角A、B、C及其对边a、b、c，满足sin（A－B）=sinB+sinC.（Ⅰ）求角A的大小；（Ⅱ）若a=6，求△ABC面积的最大值.