Help me in solving SUBS problem

My issue

The “Solution” tab doesn’t show the video that’s usually there, or any other information in it. When I run the program, it’s also not showing the test cases for which my code is not passing.

My code

for _ in range(int(input())):
    n, k = map(int, input().split())
    a = list(map(int, input().split()))
    b = a[0:k]
    print(a[k - 1] - a[0])

Learning course: Jump from 2* to 3*
Problem Link: CodeChef: Practical coding for everyone