#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#define LL long long 
using namespace std;
const int MAXN = 100050;
int a[MAXN], b[MAXN], n, m, c[MAXN];
LL calc(int pos) {
        LL ans = 0;
        int t = 1;
        for (int i = pos; i <= n; ++ i) {
                if (t <= m && a[i] >= b[t]) 
                          ans += a[i] - b[t], ++ t;
        }
        return ans;
}
void work() {
        scanf("%d%d", &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);
        c[0] = 0;
        for (int i = 1; i <= n; ++ i) {
            int la = c[i-1];
            while (la + 1 <= m && a[i] >= b[la + 1]) 
                      ++ la;
            c[i] = la;
        }
        LL ans = 0;
        int L = 0, R = n;
          while (L + 10 < R) {
            int lm = (2 * L + R) / 3, rm = (2  * R + L) / 3;
            if (calc(lm) < calc(rm)) 
                      L = lm;
            else R = rm;
        }      
        for (int i = L; i <= R; ++ i) 
                  ans = max(ans, calc(i));
        cout<<ans<<endl;
    //    int t = n + 1;
    //    while (t - 1 >= 1 && c[t-1] >= (n - (t-1) + 1)) -- t;
    /*    int t1 = n + 1, t2 = 0;
        while (t2 + 1 <= m && t1 - 1 >= 1 && a[t1 - 1] >= b[t2+1]) ++ t2, -- t1; */
    /*    LL ans = 0;
        for (int i = n; i >= t; -- i) 
                  ans += a[i];
        for (int j = 1; j <= (n - t + 1); ++ j)
                 ans -= b[j];
       cout<<ans<<endl;    */
        
}
int main() {
        //     freopen("b.in", "r", stdin);
            int T;
            scanf("%d", &T);
            while (T --) work();
            return 0;
}