You started to work as a database administrator for UEFA. You are asked to design a database to keep information $$bout European Football Leagues, including countries, leagues, teams, and players. Each league belongs to only one country, but one country may have many leagues, such as first, second, super, etc. Each player is a citizen of only one country. Historically each team has been in many leagues for some period of time, but the current league of each team is only one. Similarly, each player has played for one or many teams, but the current team of each player is only one. You can create two date attributes to save start and end dates for player$-$team and team$-$leagues pairs $($End dates will be null for current$).$ For each player, you must save how much he earned from each played team. You have to save first and last names of players and also names of countries, leagues and teams.

$1$

Draw your database's entity$-$relationship $($ER$)$ diagram by clearly showing tables, attributes, primary keys, and foreign keys. Explain your design and assumptions. $($DOC$20)$