Assume that we have four classes: Person, Teacher, Student, and PhDStudent. Teacher and Student are both subclasses of Person. PhDStudent is a subclass of Student. A.Which of the following assignments are legal, and why or why not? Person p1 = new Student(); Person p2 = new PhDStudent(); PhDStudent phd1 = new Student(); Teacher t1 = new Person(); Student s1 = new PhDStudent(); Suppose that we have the following legal declarations and assignments: Person p1 = new Person(); Person p2 = new Person(); PhDStudent phd1 = new PhDStudent(); Teacher t1 = new Teacher(); Student s1 = new Student(); B.Based on those just mentioned, which of the following assignments are legal, and why or why not? s1 = p1; s1 = p2; p1 = s1; t1 = s1; s1 = phd1; phd1 = s1;

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