#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int i,j,m,n,p,k,T,a[100005],b[100005],c[100005],l;
long long ans;
inline bool cmp(int a,int b) {return a>b; }
int main()
{
     scanf("%d",&T);
     for (;T--;)
{
     ans=0;
     scanf("%d%d",&n,&m);
     for (i=1;i<=n;++i) scanf("%d",&a[i]);
     for (i=1;i<=m;++i) scanf("%d",&b[i]);
     sort(a+1,a+n+1,cmp);
     sort(b+1,b+m+1);
     int l=0,r=min(n,m)+1,mid=0;
     for (;mid!=(l+r)>>1;)
     {
          mid=(l+r)>>1;
          if (a[mid]>=b[mid]) l=mid;
          else r=mid;
     }
     for (i=1;i<=l;++i) ans+=a[i]-b[i];
     printf("%I64d\n",ans);
}
}