#include<bits/stdc++.h>
#define ll long long
#define ull unsigned ll
#define uint unsigned
#define pii pair<int,int>
#define pll pair<ll,ll>
#define IT iterator
#define PB push_back
#define fi first
#define se second
#define For(i,j,k) for (int i=(int)(j);i<=(int)(k);i++)
#define Rep(i,j,k) for (int i=(int)(j);i>=(int)(k);i--)
#define CLR(a,v) memset(a,v,sizeof(a));
#define CPY(a,b) memcpy(a,b,sizeof(a));
#define debug puts("wzpakking")
#define y1 ysghysgsygsh 
using namespace std;

void solve(){
    int ans=1<<30,n,m;
    scanf("%d%d",&n,&m);
    For(i,1,n){
        int x,y;
        scanf("%d%d",&x,&y);
        int T=(m+x-1)/x;
        ans=min(ans,T*y);
    }
    cout<<ans<<endl;
}
int main(){
    int T;
    scanf("%d",&T);
    while (T--) solve();
}