Given is the IntNode class that represents an element in a linked list, and the IntList class that represents a linked list (at the end of the question). Add a method signed to the IntList class: public void sumPairs() The method will replace each pair of adjacent members with one member that contains the sum of the members. If the list has an odd number of members, the last member will remain as it is. For example, if the list was 1-->3-->2-->1-->5-->null then after running the method, the list will look like this: 4-->3-->5-->null