B"You are given an array a_1, a_2, ... , a_n , consisting of n integers. You are also given two integers k and x . You have to perform the following operation exactly once: add x to the elements on exactly k distinct positions, and subtract x from all the others. For example, if a = [2, -1, 2, 3] , k = 1 , x = 2 , and we have picked the first element, then after the operation the array a = [4, -3, 0, 1] . Let f(a) be the maximum possible sum of a subarray of a . The subarray of a is a contiguous part of the array a , i. xe2 x80 x89e. the array a_i, a_{i + 1}, ... , a_j for some 1 <= i <= j <= n . An empty subarray should also be considered, it has sum 0 . Let the array a' be the array a after applying the aforementioned operation. Apply the operation in such a way that f(a') is the maximum possible, and print the maximum possible value of f(a') . The first line contains a single integer t ( 1 <= t <= 10^4 ) -- the number of test cases. The first line of each test case contains three integers n , k and x ( 1 <= n <= 2 cdot 10^5 ; 0 <= k <= min(20, n) ; -10^9 <= x <= 10^9 ). The second line contains n integers a_1, a_2, ... , a_n ( -10^9 <= a_i <= 10^9 ). The sum of n over all test cases doesn't exceed 2 cdot 10^5 . For each test case, print one integer -- the maximum possible value of f(a') . "...