a) Write a Java program for a super class PlainBox, described below Description of PlainBox class: Protected Instance variables: o a string m shape: the shape of the box o a string m size: the size of the box Function members: o Constructor without parameters and constructor with parameters o Two accessors(get operation) to get the box's shape and size o a mutator(set operation) SetBox() which sets two instance variables o an overridden toString) method: returns the description of shape and size