Find the Sum of Last N nodes of the Linked List (Function Program)

Given a single linkd list of size M, your task is to complete the function sumOfLastN_Nodes(), which should return the sum of last N nodes of the linked list.

Input:
The function takes two arguments as input, the reference pointer to the head of the linked list and the an integer N.
There will be T test cases and for each test case the function will be called seperately.

Output:
For each test case output the sum of last N nodes of the linked list.

Constraints:
1<=T<=100
1<=N<=M<=1000

Example:
Input:
2
6 3
5 9 6 3 4 10
2 2
1 2
Output:
17
3



Solution in c++