#include<bits/stdc++.h>
typedef long long ll;
ll gi(){
    ll x=0,f=1;
    char ch=getchar();
    while(!isdigit(ch))f^=ch=='-',ch=getchar();
    while(isdigit(ch))x=x*10+ch-'0',ch=getchar();
    return f?x:-x;
}
std::mt19937 rnd(time(NULL));
#define rand rnd
#define pr std::pair<int,int>
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
template<class T>void cxk(T&a,T b){a=a>b?a:b;}
template<class T>void cnk(T&a,T b){a=a<b?a:b;}
#ifdef mod
int pow(int x,int y){
    int ret=1;
    while(y){
        if(y&1)ret=1ll*ret*x%mod;
        x=1ll*x*x%mod;y>>=1;
    }
    return ret;
}
template<class Ta,class Tb>void inc(Ta&a,Tb b){a=a+b>=mod?a+b-mod:a+b;}
template<class Ta,class Tb>void dec(Ta&a,Tb b){a=a>=b?a-b:a+mod-b;}
#endif
int main(){
#ifdef LOCAL
    freopen("in.in","r",stdin);
    //freopen("out.out","w",stdout);
#endif
    int qwq=gi();
    while(qwq--){
        int n=gi(),m=gi(),x,y;
        ll ans=9e18;
        for(int i=1;i<=n;++i){
            x=gi(),y=gi();
            cnk(ans,1ll*((m+x-1)/x)*y);
        }
        printf("%lld\n",ans);
    }
    return 0;
}