#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <algorithm>
using namespace std;
int _min(int x, int y) { return x < y ? x : y; }
int main() {
    int i, j, k;
    int T;
    scanf("%d", &T);
    while(T--){
        int ans = 100000000;
        int n, m;
        scanf("%d%d", &n, &m);
        for(i = 1; i <= n; i++){
            int x, y;
            scanf("%d%d", &x, &y);
            ans = _min(ans, ((m-1)/x+1)*y);
        }
        printf("%d\n", ans);
    }
    return 0;
}