题目

When Jackie Robinson walked onto Ebbets Field in Brooklyn, New York, on April 15, 1947, he changed baseball forever. As the first African American to play in the Major League in modern times, many believe he changed the country forever.     Robinson was born in 1919．He lived in a time when rules controlled what African Americans could do. He was a top athlete, playing football, basketball and baseball. But playing for a major League team was off limits to Robinson because of his race.     Branch Rickey, president and manager of the Brooklyn Dodgers, signed （和……签约） Robins小明想知道湖中两个小亭A、B之间的距离，他在与小亭A、B位于同一水平面且东西走向的湖边小道l上某一观测点M处，测得亭A在点M的北偏东30°，亭B在点M的北偏东60°，当小明由点M沿小道l向东走60米时，到达点N处，此时测得亭A恰好位于点N的正北方向，继续向东走30米时到达点Q处，此时亭B恰好位于点Q的正北方向，根据以上测量数据，请你帮助小明计算湖中两个小亭A、B之间的距离．