#include <set>
#include <map>
#include <queue>
#include <stack>
#include <cmath>
#include <string>
#include <cctype>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iomanip>
#include <iostream>
#include <algorithm>
using namespace std;
#define ls id<<1,l,mid
#define rs id<<1|1,mid+1,r
#define OFF(x) memset(x,-1,sizeof x)
#define CLR(x) memset(x,0,sizeof x)
#define MEM(x) memset(x,0x3f,sizeof x)
#define rep(i,a,b) for (int i=a;i<b;i++)
#define Rep(i,a,b) for (int i=a;i>=b;i--)
typedef long long ll ;
typedef pair<int,int> pii ;
const int maxn = 1e5+50 ;
const int inf = 0x3f3f3f3f ;
const int MOD = 1e9+7 ;
bool cmp(const int &c,const int &d) { return c > d ;}
int a[maxn],b[maxn],flag[maxn];
int m,n,t;
int main () {
#ifdef LOCAL
    freopen("C:\\Users\\Administrator\\Desktop\\in.txt","r",stdin);
#endif
    scanf("%d",&t);
    while (t--) {
        CLR(flag);
        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,cmp);
        sort(b,b+m);
        /*int j=0;
        ll ans=0;
        queue<int> q; while (!q.empty()) q.pop();
        for (int i=0;i<n;i++) {
            while (a[i]<b[i]&&j<m) j++;
            if (j>m) break;
            else ans+=a[i],q.push(j),flag[j]=1;
        }
        if (!q.empty()) for (int i=m-1;i>q.front();i--) {
            if (!flag[i]) {
                q.push(i);
                q.pop();
            }
        }
        while (!q.empty()) {
            ans-=b[q.front()];
            q.pop();
        }*/
        ll ans=0;
        for (int i=0;i<m&&i<n;i++) {
            if (a[i]<b[i]) break;
            ans+=a[i]-b[i];
        }
        printf("%I64d\n",ans);
    }
    return 0;
}