#include<bits/stdc++.h>
using namespace std;
typedef long long ll;
int tes,n,m,a[105],b[105],f[10105],ans;
int read(){
    int res=0,op=1;char ch=getchar();
    while(!isdigit(ch)){if(ch=='-')op=-1;ch=getchar();}
    while(isdigit(ch))res=res*10+ch-'0',ch=getchar();
    return res*op;
}
void write(int x){
    if(x<0)putchar('-'),x=-x;
    if(x>9)write(x/10);
    putchar(x%10+48);
}
void solve(){
    n=read(),m=read();
    for(int i=1;i<=n;i++)a[i]=read(),b[i]=read();
    ans=1e9;
    for(int i=1;i<=n;i++)ans=min(ans,((m-1)/a[i]+1)*b[i]);
    printf("%d\n",ans);
}
int main()
{
    tes=read();
    while(tes--)solve();
    return 0;
}