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

using LL = long long;
const int N = 1e5 + 5;

int n;
LL m, a[N], b[N];

void solve() {
  cin >> n >> m;
  for (int i = 1; i <= n; ++i) cin >> a[i];
  for (int i = 1; i <= n; ++i) cin >> b[i];
  int an = n;
  if (a[n] != m) a[++an] = m;
  sort(b + 1, b + n + 1);
  partial_sum(b + 1, b + n + 1, b + 1);
  int cur = n;
  while (cur && b[cur] >= m) --cur;
  LL ans = 0;
  priority_queue<LL> q;
  for (int i = an; i >= 1; --i) {
    int bck = cur;
    while (cur && b[cur] >= a[i - 1]) --cur;
    int k = bck - cur;
    while (q.size() && (k > 1 || k == 1 && a[i] - b[cur + 1] <= q.top())) {
      ans += q.top();
      q.pop();
      --k;
    }
    if (k) {
      ans += a[i] - b[cur + 1];
      if (q.size()) {
        auto v = q.top(); q.pop();
        q.push(v + b[cur + 1] - a[i - 1]);
      } else {
        q.push(b[cur + 1] - a[i - 1]);
      }
    } else q.push(a[i] - a[i - 1]);
  }
  cout << ans << "\n";
}

int main() {
  cin.tie(0)->sync_with_stdio(0);
  int t;
  cin >> t;
  while (t--) solve();
  return 0;
}