#include <bits/stdc++.h>
using namespace std;
template <typename T> void read(T &t) {
    t=0; char ch=getchar(); int f=1;
    while (ch<'0'||ch>'9') { if (ch=='-') f=-1; ch=getchar(); }
    do { (t*=10)+=ch-'0'; ch=getchar(); } while ('0'<=ch&&ch<='9'); t*=f;
}

int T,n,m,x,y,ans,tmp;

int main() {
    //freopen("1.txt","r",stdin);
    read(T);
    while (T--) {
        read(n); read(m); ans=(1e9);
        for (int i=1;i<=n;i++) {
            read(x); read(y);
            if (m%x==0) tmp=m/x*y;
            else tmp=(m/x+1)*y;
            ans=min(ans,tmp);
        }
        printf("%d\n",ans);
    }
    return 0;
}
/*
  0. Enough array size? Enough array size? Enough array size? Interger overflow?
  
  1. Think TWICE, Code ONCE!
  Are there any counterexamples to your algo?
    
  2. Be careful about the BOUNDARIES!
  N=1? P=1? Something about 0?
    
  3. Do not make STUPID MISTAKES!
  Time complexity? Memory usage? Precision error?
*/