贪心：Alice优先拿最大的，Bob也优先那最大的
Bob的策略，把每个回合的次大值增加到尽量和最大值相近

#pragma GCC optimize(2)
#pragma GCC optimize(3)
#include "bits/stdc++.h"
using namespace std;
#define ios ios::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define fios ofstream("test.txt");cout.rdbuf(out.rdbuf())
#define endl "\n"
#define INF 0x3f3f3f3f
#define MINF 2146473647
#define eps 1e-6
#define PI acos(-1)
#define lowbit(x) (x & (-x))
typedef long long LL;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
#define x first
#define y second
const int N = 200010;

int n, k;
int a[N];

bool cmp(int a, int b)
{
    return a > b;
}

int main()
{
    int T;
    cin >> T;
    while(T--)
    {
        cin >> n >> k;
        for(int i = 0; i < n; i++) cin >> a[i];
        sort(a, a + n, cmp);
        for(int i = 1; i < n; i += 2)
        {
            int d = a[i - 1] - a[i];
            if(k >= d)
            {
                a[i] = a[i - 1];
                k -= d;
            }
            else
            {
                a[i] += k;
                k = 0;
            }
        }

        int cntA = 0, cntB = 0;
        for(int i = 0; i < n; i++)
            if(i % 2) cntB += a[i];
            else cntA += a[i];

        cout << cntA - cntB << endl;
    }

    return 0;
}