D

#include <bits/stdc++.h>
using namespace std;

#define int long long

signed main(){
    int tst;
    cin>>tst;

    while(tst--){
        int n, k;
        cin >> n >> k;

        vector<pair<int, int>> c(n + 1);
        for (int i = 1; i <= n; i++) {
            cin >> c[i].second;
        }

        int res = 0;
        for (int i = 1; i <= n; i++) {
            cin >> c[i].first;
            res += max(0ll, c[i].first - c[i].second);
        }

        sort(c.begin() + 1, c.end());

        priority_queue<int> q;

        int ans = 0, sum = 0;
        for (int i = n; i; i--) {
            if (i <= n - k) {
                ans = max(ans, res - sum);
            }
            q.push(c[i].second);
            sum += c[i].second;
            if (q.size() > k) {
                sum -= q.top();
                q.pop();
            }

            res -= max(0ll, c[i].first - c[i].second);
        }

        cout << ans << "\n";
    }
}