#include <iostream>
#include <vector>
#include <algorithm>
#include <cstring>
#include <map>
#include <sstream>
using namespace std;

void process() {
    int n, m;
    cin >> n >> m;

    int ans = -1;
    for (int i = 0; i < n; ++i) {
        int x, y;
        cin >> x >> y;

        int t = (m + x - 1) / x * y;
        if (ans == -1 || t < ans) ans = t;
    }

    cout << ans << endl;


    /*
    int n;
    cin >> n;
    vector<int> nums(n);

    string s;
    // NOTE: if using getline() to read the input, the following two lines should be
    // added to read the line sepeartor in the first line. 
    getline(cin, s);

    getline(cin, s);
    stringstream S(s);
    */
}

int main(void) {
    int T;
    cin >> T;
    for (int i = 1; i <= T; ++i) {
        process();
    }
    return 0;
}