The Book class constructor has the following signature:

public Book(String author, int numPages)

Write the class wrapper and constructor for a class called ReferenceBook which is a direct subclass of Book and which contains one String field specifying a subjectArea. The ReferenceBook constructor takes three parameters: the author, the number of pages, and the subject area. The ReferenceBook constructor's statements must cause a new ReferenceBook object to be initialized with author, pages, and area.