Given a single linked 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
Explanation:
Testcase 1: Sum of last three nodes in the linked list is 3 + 4 + 10 = 17.

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