#include <stdio.h>
#include <string.h>
#include <iostream>
#include <algorithm>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <string>
#include <math.h>
#include <stdlib.h>
#include <time.h>
using namespace std;
const int maxn = 1e5+5;
int a[maxn], b[maxn];
int n, m;

int main()
{
    //freopen("out", "w", stdout);
    //freopen("in", "r", stdin);
    int cases;
    scanf("%d", &cases);
    while(cases--) {
        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);
        long long ans = 0;
        int k = 0;
        for(int i = n-1; i >= 0; --i) {
            if(k == m) break;
            if(a[i]-b[k] < 0) break;
            ans += a[i]-b[k++];
        }
        printf("%I64d\n", ans);
    }
    return 0;
}