#include <cstdio>
#include <algorithm>
#include <cstring>
using namespace std;

const int N = 1e4 + 100;

int n, m;
int xx[N], yy[N];
int dp[N];

void upd(int &x, int y) {
    x = min(x, y);
}

int main() {
    int T;
    scanf("%d", &T);
    while (T--) {
        scanf("%d%d", &n, &m);
        int ans = 1e9;
        for (int i = 1; i <= n; i++) {
            scanf("%d%d", xx + i, yy + i);
            int t = m / xx[i];
            if (t * xx[i] < m) t++;
            ans = min(ans, t * yy[i]);
        }
        printf("%d\n", ans);
        
    }
    return 0;
}