#include<bits/stdc++.h>
#define MAXN 100005
#define INF 1000000000
#define MOD 1000000007
#define F first
#define S second
using namespace std;
typedef long long ll;
typedef pair<int,int> P;
int t,n,m,a[MAXN],b[MAXN];
int main()
{
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d",&n,&m);
        for(int i=1;i<=n;i++) scanf("%d%d",&a[i],&b[i]);
        int ans=INF;
        for(int i=1;i<=n;i++) ans=min(ans,(m+a[i]-1)/a[i]*b[i]);
        printf("%d\n",ans);
    }
}