#include <bits/stdc++.h>
using namespace std;
void itval(istream_iterator<string> it) {}
template <typename T, typename... Args>
void itval(istream_iterator<string> it, T a, Args... args) {
  cerr << *it << " = " << a << endl;
  itval(++it, args...);
}
const long long int MOD = 1e9 + 7;
template <typename T>
inline void print(T x) {
  cout << x << "\n";
}
template <typename T>
inline void printvec(T x) {
  for (auto a : x) cout << a << ' ';
  cout << '\n';
}
struct custom {
  bool operator()(const pair<int, int> &p1, const pair<int, int> &p2) const {
    return p1.first + p2.second < p1.second + p2.first;
  }
};
long long int get_pow(long long int a, long long int b, long long int M) {
  long long int res = 1;
  while (b) {
    if (b & 1) res = (res * a) % M;
    a = (a * a) % M;
    b >>= 1;
  }
  return res;
}
const long long int N = 1e5 + 5, inf = 2e18;
void solve() {
  long long int n, s;
  cin >> n >> s;
  std::vector<pair<long long int, long long int> > v(n);
  for (long long int i = (long long int)0; i < (long long int)(n); i++) {
    cin >> v[i].first >> v[i].second;
  }
  sort(v.begin(), v.end());
  long long int lo = 0, hi = 1e9 + 5;
  while (lo + 1 < hi) {
    long long int mid = (lo + hi) / 2;
    long long int sum = 0, m = n / 2, ok = 1, cnt = 0, c = 0;
    vector<bool> used(n, false);
    long long int l = 0, h = 0;
    for (long long int i = (long long int)0; i < (long long int)(n); i++) {
      if (v[i].second < mid) {
        sum += v[i].first;
        used[i] = 1;
        l++;
      }
      if (v[i].first > mid) {
        sum += v[i].first;
        used[i] = 1;
        h++;
      }
    }
    if (l > n / 2 || h > n / 2) ok = 0;
    if (l > n / 2) {
      hi = mid;
      continue;
    }
    if (h > n / 2) {
      lo = mid;
      continue;
    }
    if (ok) {
      for (long long int i = (long long int)0; i < (long long int)(n); i++) {
        if (used[i]) continue;
        if (l < n / 2) {
          sum += v[i].first;
          l++;
          continue;
        }
        if (h < n / 2) {
          sum += mid;
          h++;
          continue;
        }
      }
      sum += mid;
      if (sum > s) ok = 0;
    }
    if (ok)
      lo = mid;
    else
      hi = mid;
  }
  cout << lo << '\n';
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  int test = 1;
  cin >> test;
  clock_t z = clock();
  for (long long int tes = (long long int)0; tes < (long long int)(test);
       tes++) {
    solve();
  }
  fprintf(stderr, "Total Time:%.4f\n", (double)(clock() - z) / CLOCKS_PER_SEC),
      fflush(stderr);
  return 0;
}
