#include <iostream>
#include <cstring>
#include <cstdio>
#define maxn 105

using namespace std;

int n,m,x[maxn],y[maxn];
int dp[10105];

int main()
{
    int T;
    scanf("%d",&T);
    while (T--)
    {
        memset(dp,0x3f,sizeof(dp));
        int M=dp[0];
        scanf("%d%d",&n,&m);
        int ans=0x7fffffff;
        for (int i=0;i<n;i++)
        {
            scanf("%d%d",&x[i],&y[i]);
            int ti=(m/x[i])+(m%x[i]? 1:0 );
            ans=min(ans,ti*y[i]);
        }
        printf("%d\n",ans);
    }
    return 0;
}