#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <vector>

using namespace std;

#define print(x) cout << x << endl
#define input(x) cin >> x

typedef long long llint;

const int INF = 0x3f3f3f3f;

struct Drink {
    int water, energy;
};

int main() {
    int T;
    input(T);

    while (T--) {
        int n, m;
        scanf("%d%d", &n, &m);

        int ans = INF;
        vector<Drink> ds(n);
        for (int i = 0; i < n; i++) {
            scanf("%d%d", &ds[i].water, &ds[i].energy);
            ans = min(ans, (m + ds[i].water - 1) / ds[i].water * ds[i].energy);
        }

        printf("%d\n", ans);
    }

    return 0;
}