#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<iostream>
#include<queue>
#include<set>
#include<map>
using namespace std;

typedef long long ll;
const int N = 106;

int main()
{
    int t, n, m, i, x, y;
    scanf("%d", &t);
    while(t--){
        int tp, minn = 0x3f3f3f3f;
        scanf("%d%d", &n, &m);
        for(i = 0; i < n; ++i){
            scanf("%d%d", &x, &y);
            tp = m/x;
            if(tp*x == m)
                tp *= y;
            else
                tp = (tp+1)*y;
            if(minn > tp)
                minn = tp;
        }
        printf("%d\n", minn);
    }
    return 0;
}