#include<bits/stdc++.h>
#define rep(i, l, r) for(int i = (l), i##end = (r);i <= i##end;++i)
using std::cin;
using std::cout;
using u32 = unsigned;
using u64 = unsigned long long;
using ll = long long;

int n, m;
const int N = 2010;
int main() {
    std::ios::sync_with_stdio(false), cin.tie(0);
    int test;
    cin >> test;
    for(int i = 0;i < test;++i) {
        cin >> n >> m;
        int ans = 1e9;
        for(int i = 0, x, y;i < n;++i) {
            cin >> x >> y;
            ans = std::min(ans, (m + x - 1) / x * y);
        }
        cout << ans << '\n';
    }
}