#pragma GCC optimize(2)
#pragma GCC optimize("Ofast","unroll-loops","omit-frame-pointer","inline")
#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll,ll>PLL;
typedef pair<int,int>PII;
typedef pair<double,double>PDD;
#define I_int ll
#define modl 19260817*19890604-19491001
inline ll read()
{
    ll x=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();}
    while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
    return x*f;
}
char F[200];
inline void out(I_int x) {
    if (x == 0) return (void) (putchar('0'));
    I_int tmp = x > 0 ? x : -x;
    if (x < 0) putchar('-');
    int cnt = 0;
    while (tmp > 0) {
        F[cnt++] = tmp % 10 + '0';
        tmp /= 10;
    }
    while (cnt > 0) putchar(F[--cnt]);
    //cout<<" ";
}
const int maxn=11000;

int x[maxn],y[maxn];

int main(){
    int T=read();
    while(T--){
        int n=read(),m=read();
        for(int i=1;i<=n;i++) x[i]=read(),y[i]=read();
        int minn=1e9;
        for(int i=1;i<=n;i++){
            int tmp=m/x[i];
            if(m%x[i]) tmp++;
            minn=min(minn,tmp*y[i]);
        }
        cout<<minn<<endl;
    }
    return 0;
}