#include<iostream>
#include<algorithm>
#include<cmath>
#include<cstring>

typedef long long ll;
using namespace std;

int main()
{
    int t;
    cin >> t;
    while (t--) {
        ll n, m, i, k, x, y;
        ll sum, min=9999999999999, j=0;
        cin >> n >> m;
        for (i = 0; i < n; i++) {
            cin >> x >> y;

            k = m / x;
            if (k * x != m) {
                j = (k + 1) * y;
            }
            else {
                j = k * y;
            }
            if (j < min) {
                min = j;
            }
        }
        cout << min << endl;
    }
    return 0;
}