def max_number(arr, k):
    n = len(arr)
    for _ in range(k):
        max_idx = -1
        for i in range(n - 1):
            if str(arr[i]) + str(arr[i + 1]) > str(arr[i + 1]) + str(arr[i]):
                max_idx = i
                break
        if max_idx == -1:
            break
        arr[max_idx] = str(arr[max_idx]) + str(arr[max_idx + 1])
        arr.pop(max_idx + 1)
        n -= 1
    return int(arr[0])

t = int(input())
for _ in range(t):
    n, k = map(int, input().split())
    arr = list(map(int, input().split()))
    print(max_number(arr, k))