#include<iostream>

#include<cstdio>

#include<cstring>

#include<string>

#include<algorithm>

#include<cctype>

#include<cmath>

#include<cstdlib>

#include<queue>

#include<ctime>

#include<vector>

#include<set>

#include<map>

#include<stack>

using namespace std;

int a[],b[];

inline int ra(){

    int x=,f=;char s=getchar();

    while(!isdigit(s)){if(s=='-')f=-;s=getchar();}

    while(isdigit(s))x=(x<<)+(x<<)+(s-''),s=getchar();

    return x*f;

}

int main(){

    int n,m,i,j,k,t;

    scanf("%d",&t);

    while(t--){

      long long Ans=;

      scanf("%d%d",&n,&m);

      for(i=;i<=n;i++)a[i]=ra();

      for(i=;i<=m;i++)b[i]=ra();

      sort(a+,a+n+);

      sort(b+,b+m+);

      i=n;j=;

      while(i>&&j<=m){

          if(a[i]>b[j]){

            Ans+=(a[i]-b[j]);

          i--,j++;

        }else break;

      }

      printf("%lld\n",Ans);

    }

    return ;

}