#include<bits/stdc++.h>
using namespace std;
#define REP(i,st,ed) for(register int i=st,i##end=ed;i<=i##end;++i)
#define DREP(i,st,ed) for(register int i=st,i##end=ed;i>=i##end;--i)
template<typename T>inline bool chkmin(T &x,T y){return (y<x)?(x=y,1):0;}
template<typename T>inline bool chkmax(T &x,T y){return (y>x)?(x=y,1):0;}
typedef long long ll;
inline int read(){
    static int x,f;f=1;
    static char c;
    while((c=getchar())!='-' && (c>'9' || c<'0'));
    if(c=='-') f=-1,c=getchar();
    x=(c^'0');
    while((c=getchar())>='0' && c<='9') x=(x<<1)+(x<<3)+(c^'0');
    return x*f;
}
int main(){
    int T=read();
    while(T--){
        int n=read(),m=read();
        int Min=1e9;
        REP(i,1,n){
            int x=read(),y=read();
            chkmin(Min,((m-1)/x+1)*y);
        }
        printf("%d\n",Min);
    }
    return 0;
}