Which Dodgers executive signed Jackie Robinson?

Which Negro Leagues pitching legend made his MLB debut with Cleveland at age 42 in 1948? Who founded the Negro National League in 1920? Which Negro Leagues star was famed as perhaps the fastest player in baseball history? Which Negro Leagues player and manager later became MLB's first Black coach, with the Cubs in 1962? Who became MLB's first Black manager, with Cleveland in 1975? How far is the pitching rubber from home plate? How many games does each MLB team play in a regular season? In which year did the American League adopt the designated hitter?