#include <cstdio>
#include <iostream>
#include <algorithm>
using namespace std;

typedef long long LL;
const int N = 131420;

int a[N], b[N];

int main() {
    int n, m, T;

    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &n, &m);
        for (int i = 0; i < n; ++i) {
            scanf("%d", a + i);
        }
        for (int i = 0; i < m; ++i) {
            scanf("%d", b + i);
        }
        sort(a, a + n);
        sort(b, b + m);
        LL answer = 0;

        for (int i = n - 1, j = 0; i >= 0 && j < m && a[i] > b[j]; --i, ++j) {
            answer += a[i] - b[j];
        }
        cout << answer << endl;
    }

    return 0;
}