#include <bits/stdc++.h>
using namespace std;
const long double pi = 3.14159265358979323;
long long mod = 1000000000 + 7;
long long modu = 998244353;
const long double pii = acos(-1.0);
const long long INF = 1e18;
const long long inf = 1e9;
long long power(long long x, long long y) {
  long long res = 1;
  x = x;
  while (y > 0) {
    if (y & 1) res = (res * x);
    y = y >> 1;
    x = (x * x);
  }
  return res;
}
long long powe(long long x, long long y) {
  x = x % mod, y = y % (mod - 1);
  long long ans = 1;
  while (y > 0) {
    if (y & 1) {
      ans = (1ll * x * ans) % mod;
    }
    y >>= 1;
    x = (1ll * x * x) % mod;
  }
  return ans;
}
long long gcd(long long a, long long b) {
  if (a == 0) return b;
  return gcd(b % a, a);
}
long long lcm(long long a, long long b) { return (a / gcd(a, b) * b); }
bool isPrime(long long n) {
  if (n < 2) return false;
  for (long long i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
long long ncr(long long n, long long r) {
  long long res = 1;
  if (r > n) return 0;
  if (r > n - r) r = n - r;
  for (long long i = 0; i < r; i++) {
    res *= (n - i);
    res /= (i + 1);
  }
  return res;
}
long long add(long long a, long long b) { return ((a % mod + b % mod) % mod); }
long long sub(long long a, long long b) {
  return ((a % mod - b % mod + mod) % mod);
}
long long mul(long long a, long long b) {
  return (((a % mod) * (b % mod)) % mod);
}
long long divi(long long a, long long b) {
  return (mul(a, powe(b, mod - 2)) % mod);
}
void fun() {}
const long long N = 2e9 + 7;
void pre() {}
bool ok(long long mid, long long s, std::vector<pair<long long, long long> > v,
        long long n) {
  long long cnt = 0;
  long long avail = s;
  for (long long i = 0; i < n; i++) {
    if (v[i].second >= mid) cnt++;
  }
  if (cnt < (n + 1) / 2) return false;
  long long ans = 0;
  for (long long i = n - 1; i >= 0; i--) {
    if (v[i].second >= mid)
      avail -= max(v[i].first, mid), ans++, v[i].first = -1;
    if (ans == (n + 1) / 2) break;
  }
  for (long long i = 0; i < n; i++) {
    if (v[i].first == -1) continue;
    avail -= v[i].first;
  }
  return (avail >= 0);
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  ;
  fun();
  pre();
  long long tttt = 1;
  cin >> tttt;
  while (tttt--) {
    long long n, s;
    cin >> n >> s;
    std::vector<pair<long long, long long> > v;
    for (long long i = 0; i < n; i++) {
      long long l, r;
      cin >> l >> r;
      v.push_back(make_pair(l, r));
    }
    if (n == 1) {
      cout << min(s, v[0].second) << "\n";
      continue;
    }
    sort(v.begin(), v.end());
    long long ans = 0;
    long long hi = inf, lo = 0;
    while (hi >= lo) {
      long long mid = (hi + lo) >> 1;
      if (ok(mid, s, v, n))
        ans = mid, lo = mid + 1;
      else
        hi = mid - 1;
    }
    cout << ans << "\n";
  }
  cerr << "time elapsed : " << 1.0 * clock() / CLOCKS_PER_SEC << " sec \n";
  return 0;
}
