#include <bits/stdc++.h>
using namespace std;
struct Data {
  long long l, r;
} a[200100];
long long n, s, rmax, lmin;
void Docfile() {
  scanf("%lld%lld", &n, &s);
  rmax = 0;
  lmin = 1e18;
  for (int i = 1; i <= n; i++) {
    scanf("%lld%lld", &a[i].l, &a[i].r);
    rmax = max(rmax, a[i].r);
    lmin = min(lmin, a[i].l);
  }
}
bool cmp(Data &a, Data &b) {
  return ((a.l < b.l) || ((a.l == b.l) && (a.r < b.r)));
}
void Xuli() {
  sort(a + 1, a + 1 + n, cmp);
  long long sum1, sum2, dem1, dem2, dem3, F[200100];
  long long d = lmin, c = rmax, g, kq = 0;
  while (d <= c) {
    g = (d + c) / 2;
    dem1 = dem2 = dem3 = sum1 = sum2 = 0;
    F[0] = 0;
    for (int i = 1; i <= n; i++) {
      if (a[i].r < g) {
        dem1++;
        sum1 += a[i].l;
      } else {
        if (a[i].l > g) {
          dem2++;
          sum2 += a[i].l;
        } else {
          dem3++;
          F[dem3] = F[dem3 - 1] + a[i].l;
        }
      }
    }
    if (dem1 > n / 2) {
      c = g - 1;
      continue;
    }
    if (dem2 > n / 2) {
      d = g + 1;
      continue;
    }
    if (dem1 < n / 2) sum1 += F[n / 2 - dem1];
    if (dem2 < n / 2) sum2 += g * (n / 2 - dem2);
    if (sum1 + sum2 + g <= s) {
      kq = max(kq, g);
      d = g + 1;
    } else
      c = g - 1;
  }
  printf("%lld\n", kq);
}
int main() {
  long t;
  scanf("%d", &t);
  for (int i = 1; i <= t; i++) {
    Docfile();
    Xuli();
  }
}
