M$3$: Identify attributes and attribute typesM$3$: Identify unique identifiers for each entity

The Fresno Baseball League wants to maintain information about its teams, their coaches, players, and bats. The information about players is historical. For each team, the league wants to keep track of all of the players who have ever played on the team, including the current players. For each player, it wants to know about every team the player ever played for. On the other hand, coach affiliation and bat information is only current.The league wants to keep track of each team's team number, which is unique, its name, the city in which it is based, and the name of its manager. Coaches have a name $($which is assumed to be unique only within its team$)$ and a telephone number. Coaches have units of work experience that are described by the type of experience and the number of years of that type of experience. Bats are described by their serial numbers $($which are unique only within a team$)$ and their manufacturer's name. Players have a player number that is unique across the league, a name, and an age.A team has at least one and usually several coaches. A coach works for only one team. Each coach has several units of work experience or may have none. Each unit of work experience is associated with the coach to whom it belongs. Each team owns at least one and generally many bats. Currently and historically, each team has and has had many players. To be of interest to the league, a player must have played on at least one and possibly many teams during his career. Further, the league wants to keep track of the number of years that a player has played on a team and the batting average that he compiled on that team.