#include<bits/stdc++.h>
inline int read(){
    int x=0,w=1;
    char ch=0;
    while (ch<'0' || ch>'9'){
        ch=getchar();
        if (ch=='-') w=-1;    
    }
    while (ch<='9' && ch>='0'){
        x=(x<<1)+(x<<3)+ch-'0';
        ch=getchar();
    }
    return x*w;
}
using namespace std;
typedef long long ll;
const int N=1e5+5;
int main(){
    int T=read();
    while (T--){
        int n=read(),m=read(),ans=1e9;
        for (int i=1;i<=n;++i){
            int x=read(),y=read();
            ans=min(ans,(m/x+(m%x!=0))*y);
        }
        printf("%d\n",ans);
    }
    return 0;
}