#include <bits/stdc++.h>

using namespace std;

int test, n, m, x, y, ans;

int main() {
  scanf("%d", &test);
  while (test--) {
    scanf("%d%d", &n, &m);
    ans = 1e9;
    while (n--) {
      scanf("%d%d", &x, &y);
      ans = min(ans, ((m - 1) / x + 1) * y);
    }
    printf("%d\n", ans);
  }
  return 0;
}