#include <cstdio>
#include <algorithm>
using namespace std;
typedef long long ll;
const int maxn = 100000 + 10;
int a[maxn] , b[maxn];
int main() {
    int T;
    scanf("%d",&T);
    while(T--) {
        int n , m;
        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);
        int pa = n-1 , pb = 0;
        ll ans = 0;
        while(pa >= 0 && pb < m) {
            if(a[pa] > b[pb]) {
                ans += (a[pa]-b[pb]);
                pa-- , pb++;
            }
            if(a[pa] <= b[pb]) break;
        }
        printf("%I64d\n",ans);
    }
    return 0;
}