#include <iostream>
#include <algorithm>
#include <unordered_map>
#include <string>
#include <vector>
#include <map>
#include <cassert>

using namespace std;
 
void work() {
    int n, m;
    cin >> n >> m;
    long long res = 10000000000000;
    for (int i = 0; i < n; ++i) {
        long long x, y;
        cin >> x >> y;
        int t = m / x;
        if (m%x) ++t;
        long long v = t * y;
        res = min(res, v);
    }
    cout << res << endl;
}

int main() {
    cin.sync_with_stdio(0); cin.tie(0); cout.tie(0); // close sync between cout and printf
    int T;
    cin >> T;
    for (int ii=1; ii<=T; ++ii) {
        work();
    }
    return 0;
}