#include <bits/stdc++.h>
using namespace std;
const long long infl = 0x3f3f3f3f3f3f3f3fLL;
const long long infi = 0x3f3f3f3f;
const long long mod = infl;
long long mygcd(long long a, long long b) {
  if (b == 0) {
    return a;
  }
  return mygcd(b, a % b);
}
long long mypow(long long a, long long b) {
  long long res = 1;
  while (b) {
    if (b & 1) res = (res * a) % mod;
    a = (a * a) % mod;
    b >>= 1;
  }
  return res;
}
void solve() {
  long long n, k;
  cin >> n >> k;
  vector<long long> a(n), b(n);
  for (long long i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (long long i = 0; i < n; i++) {
    cin >> b[i];
  }
  sort(a.begin(), a.end());
  sort(b.begin(), b.end());
  reverse(b.begin(), b.end());
  for (long long i = 0; i < k; i++) {
    if (a[i] < b[i]) {
      a[i] = b[i];
    }
  }
  cout << accumulate(a.begin(), a.end(), 0ll) << '\n';
}
signed main() {
  ios_base::sync_with_stdio(false);
  cout << fixed << setprecision(20);
  cin.tie(NULL);
  long long t = 1;
  cin >> t;
  while (t--) {
    solve();
  }
  return 0;
}
