#include<cstdio>
#include<algorithm>
#define maxn 105
#define maxm 20550
using namespace std;

int n,m;
int x[maxn],y[maxn];

const int inf=1e9;

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