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

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int tt;
  cin >> tt;
  while(tt--) {
    int n, m;
    cin >> n >> m;
    int64_t ans = 0;
    vector<int> a(n), b(n);
    vector<int> A, B;
    for (int i =0; i < n; i++) {
      cin >> a[i] >> b[i];
      if (a[i] >= b[i]) {
        B.push_back(i);
      } else {
        A.push_back(i);
      }
    }
    sort(A.begin(), A.end(), [&](int x, int y){
      return a[x] > a[y];
    });
    int s = min(m - n, (int)A.size());
    if (s + 1 == A.size() && B.size() == 0) {
      // Everyone is separate.
      for (int i =0; i < n; i++) {
        ans += b[i];
      }
      cout << ans << '\n';
      continue;
    }
    if (s == A.size() && B.size() == 1) {
      if (A.size() == 0) {
        // all alone
        cout << b[0] << '\n';
        continue;
      }

      // decide which to choose
      int64_t X = 0, Y =0;
      for (int i =0; i < n; i++) X += b[i];
      for (int i = 0; i + 1 < A.size(); i++) Y += b[A[i]];
      Y += a[A.back()] + a[B[0]];
      cout << max(X, Y) << '\n';
      continue;
    }
    
    // Everyone gets what they want.
    for (int i =0; i < min(s, (int)A.size()); i++) {
      ans += b[A[i]];
    }
    for (int i = s; i < A.size(); i++) ans += a[A[i]];
    for (auto&x : B) ans += a[x];
    cout << ans << '\n';
  }
}