#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
class Solution {
public:
    void print_vec(vector<int> &vec) {
        for (auto n : vec) {
            cout << n << ' ';
        }
        cout << endl;
    }
    void readdata() {
        int groups, res,p;
        vector<int> x, y, res2;
        int x2, y2;
        cin >> groups;
        while (groups) {
            int n, m;
            cin >> n >> m;
            //cout << 'n' << n << 'm' << m << endl;
            x.clear(); y.clear();
            
            p = n;
            while (p) {
                cin >> x2 >> y2;
                //cout << 'x' << x2 << 'y' << y2 << endl;
                x.push_back(x2);
                y.push_back(y2);
                p--;
            }
            res = INT_MAX;
            for (int i = 0;i<n;++i) {
                int num;
                if (m%x[i]) {
                    num = m / x[i] + 1;
                }
                else
                    num = m / x[i];
                res = min(res, num*y[i]);
            }
            res2.push_back(res);
            //cout << res;
            groups--;
        }
        for (auto n : res2) {
            cout << n << endl;
        }
    }
    
};
int main()
{
    Solution s;
    s.readdata();
    system("pause");
    return 0;
}