#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
int n, m;
int x[110], y[110];
struct node {
    int x, y;//水分和卡路里
}arr[105];
bool cmp(node a, node b) {
    return a.x / a.y > b.x / b.y;
}
int main() {
    int test,ans;
    cin >> test;
    while (test--) {
        cin >> n >> m;
        for (int i = 0; i < n; i++) {
            cin >> arr[i].x >> arr[i].y;
        }sort(arr, arr + n, cmp);
        if (m%arr[0].x == 0) {
            cout << (m / arr[0].x)*arr[0].y << endl;
        }
        else {
            cout << (m / arr[0].x + 1)*arr[0].y << endl;
        }
    }
    return 0;
}