Notice the keyword open before the base class

Notice, the keyword open before the base class Employee, it's important.
Overriding Member Functions and Properties
If the base class and the derived class have member functions or properties with
the same name :
Calling Members of Base Class from Derived Class
Member functions of the base class can be called from a derived class using
super keyword.
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In string templates, a variable is embedded by prefixing with a dollar __
Which feature of Kotlin helps to extend a class with new functionality without
Member functions of the base class can be called from a derived class using

}
}
If a variable is declared private, it is visible inside the class and its
Constructors of the derived class calls the corresponding constructor of the