#include <algorithm>
#include <cassert>
#include <cstdint>
#include <functional>
#include <iostream>
#include <iterator>
#include <numeric>
#include <vector>

std::int64_t NChoose2(const int n) { return std::int64_t{n} * (n - 1) / 2; }

// <WA>
// 最後の改行を2回している。
std::int64_t Solve(const int m,
                   const std::vector<int>& l, const std::vector<int>& r) {
  const int n = l.size();
  assert(std::ssize(r) == n);

  std::vector<int> order(n * 2);
  std::iota(order.begin(), order.end(), 0);
  std::ranges::stable_sort(
      order, {},
      [n, &l, &r](const int i) -> int { return i < n ? l[i] : r[i - n]; });
  assert(order.back() >= n);

  std::int64_t length = std::reduce(l.begin(), l.end(), INT64_C(0));
  if (length > m) return -1;
  std::int64_t ans = std::transform_reduce(
      l.begin(), l.end(), INT64_C(0), std::plus<std::int64_t>(), NChoose2);
  if (length == m) return NChoose2(m) - ans;

  int optional_values = 0;
  for (int i = 0; i < n * 2; ++i) {
    if (order[i] < n) {
      const int index = order[i];
      length -= l[index];
      ans -= NChoose2(l[index]);
      ++optional_values;
    } else {
      const int index = order[i] - n;
      length += r[index];
      assert(length <= m);
      ans += NChoose2(r[index]);
      --optional_values;
    }
    if (i + 1 < n * 2) {
      const int next_v = (order[i + 1] < n ?
                          l[order[i + 1]] : r[order[i + 1] - n]);
      if (length + std::int64_t{next_v} * optional_values >= m) {
        assert(optional_values > 0);
        const int t0 = (m - length + optional_values - 1) / optional_values - 1;
        assert((order[i] < n ? l[order[i]] : r[order[i] - n]) <= t0 &&
               t0 < next_v);
        const int num_of_t0 = (t0 + 1) * optional_values - (m - length);
        assert(0 <= num_of_t0 && num_of_t0 < optional_values);
        ans += NChoose2(t0) * num_of_t0;
        ans += NChoose2(t0 + 1) * (optional_values - num_of_t0);
        return NChoose2(m) - ans;
      }
    }
  }

  assert(length == std::reduce(r.begin(), r.end(), INT64_C(0)) && length < m);
  return -1;
}

int main() {
  constexpr int kMaxT = 200000, kMaxN = 200000, kMaxM = 1000000000;

  int t;
  std::cin >> t;
  assert(1 <= t && t <= kMaxT);

  while (t--) {
    int n, m;
    std::cin >> n >> m;
    assert(1 <= n && n <= kMaxN && 1 <= m && m <= kMaxM);
    std::vector<int> l(n);
    for (int i = 0; i < n; ++i) {
      std::cin >> l[i];
    }
    std::vector<int> r(n);
    for (int i = 0; i < n; ++i) {
      std::cin >> r[i];
      assert(0 <= l[i] && l[i] <= r[i] && r[i] <= kMaxM);
    }
    std::cout << Solve(m, l, r) << '\n';
  }
  std::cout << '\n';
  return 0;
}