#include<stdio.h>
int main()
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        int n,m;
        scanf("%d%d",&n,&m);
        int ans=1000000000;
        while(n--)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            int ans1=(m+x-1)/x*y;
            if(ans1<ans)
            {
                ans=ans1;
            }
        }
        printf("%d\n",ans);
    }
    return 0;
}