Create a Mattress class should have fields for size (king, queen, twin), manufacturer, and price, and a constructor should set default values for each. Write set methods only for size and manufacturer. The set method for size adds $200 for king or $100 for queen. Add a toString() method that returns the data from all of the fields.

A child class named AdjustableMattress extends Mattress and adds a field for adjustment type (air or mechanical), with air being the default. Include a get and set method for this field, adding $400 for air and $500 for mechanical. Implement a constructor that accepts all fields and calls the Mattress constructor. A toString() method should call the parent class toString() and add to it the adjustment type.

An application named MattressDemo should thoroughly demonstrate the functionality of both classes.