#include<bits/stdc++.h>
#define LL long long
#define dl double
template <class T>
void rd(T &x){
  x=0;T f=1;char ch=getchar();
  while(ch<'0' || ch>'9'){if(ch=='-')f=-1;ch=getchar();}
  while(ch<='9' && ch>='0')x=x*10+ch-'0',ch=getchar();x*=f;
}
using namespace std;

const int N=105;

int T,n,m;
int x[N],y[N];

int main(){
 // freopen("in.txt","r",stdin);
 // freopen("o.txt","w",stdout);
 rd(T);
 while(T--){
  rd(n);rd(m);
  for(int i=1;i<=n;i++)rd(x[i]),rd(y[i]);
  int mn=0x7fffffff;
  for(int i=1;i<=n;i++){
   mn=min(mn,((m-1)/x[i]+1)*y[i]);
  }
  printf("%d\n",mn);
 }
 return 0;
}
/**/