//Δ_1001
#include<iostream>
#include<cstdio>
#include<fstream>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<bitset>
#include<cmath>
#include<cstring>
#include<cstdlib>
using namespace std;
typedef long long LL;
typedef double DB;
const int N = 11111;
const int inf = 1e9;
void cmin(int&x,int y){
    if(x>y)
        x=y;
}
int main()
{
    int T,n,m,x,y,o;
    cin>>T;
    while(T--){
        cin>>n>>m;
        o=inf;
        while(n--){
            cin>>x>>y;
            cmin(o,((m-1)/x+1)*y);
        }
        cout<<o<<endl;
    }
    return 0;
}