#include <bits/stdc++.h>
#define inf 0x3f3f3f3f

using namespace std;

typedef long long ll;

int main() {
  int cases;
  scanf("%d",&cases);
  for(;cases;cases--) {
      int n,m;
      scanf("%d%d",&n,&m);
      int ans=inf;
      for(int i=1;i<=n;i++) {
          int x,y;
          scanf("%d%d",&x,&y);
          ans=min(ans,(m+x-1)/x*y);
      }
    printf("%d\n",ans);
  }
  return 0;
}