Model the following cases by ER diagrams. Identify the keys, attributes and relationship cardinalities, and convert them into table schemas. Provide...

Model the following cases by ER diagrams. Identify the keys, attributes and relationship cardinalities, and convert them into table schemas. Provide necessary assumptions to support your model. [1] The following descriptions are about the employee information of companies a) Each company operates 4 departments, and each department belongs to one company. Each company has a unique name, and each department has a unique number and name b) Each department employs one or more employees, and each employee works for one department. Each employee has a number, name, date of birth, and age. c) Each of the employees may have one or more dependents, and each dependent belongs to one employee. Each dependent has a name, relationship to employee, and contact telephone numbers. d) Each employee may have an employment history. Each employment history has the name of the organization that the employee worked for and in what capacity, and the start date and finish date for each employment.