#include<cstdio>
#include<cassert>
#include<algorithm>
#include<cstring>
#include<iostream>
#include<cstdlib>
#include<cmath>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<bitset>
using namespace std;
typedef long long ll;
typedef double db;
const db pi=acos(-1);
void gn(int &x){
    int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-');
    if(c=='-')sg=-1,x=0;else x=c-'0';
    while((c=getchar())>='0'&&c<='9')x=x*10+c-'0';
    x*=sg;
}
void gn(ll &x){
    int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-');
    if(c=='-')sg=-1,x=0;else x=c-'0';
    while((c=getchar())>='0'&&c<='9')x=x*10+c-'0';
    x*=sg;
}
const int mo=1000000007;
int qp(int a,ll b){int ans=1;do{if(b&1)ans=1ll*ans*a%mo;a=1ll*a*a%mo;}while(b>>=1);return ans;}


int tes;
int n,m;
int a[111111],b[111111];

int check(int k){
    for (int i=1;i<=k;i++)if(b[i]>a[n-k+i])return 0;
    return 1;
}
ll ax[111111],bx[111111];
int main()
{
    scanf("%d",&tes);
    while(tes--){
        scanf("%d%d",&n,&m);
        int lef=0,rig=min(n,m);
        for (int i=1;i<=n;i++)scanf("%d",&a[i]);
        for (int i=1;i<=m;i++)scanf("%d",&b[i]);
        sort(a+1,a+1+n);
        sort(b+1,b+1+m);
        while(lef<=rig){
            int mid=lef+rig;
            if(check(mid))lef=mid+1;
            else rig=mid-1;
        }
        ax[0]=bx[0]=0;
        for (int i=1;i<=m;i++)bx[i]=bx[i-1]+b[i];
        for (int i=1;i<=n;i++)ax[i]=ax[i-1]+a[n-i+1];
        ll su=0;
        for (int i=1;i<=rig;i++)su=max(su,ax[i]-bx[i]);
        cout<<su<<endl;
    }
    return 0;
}