#include <stdio.h>
#include <algorithm>

using namespace std;

int n , m;
int x[1200] , y[1200];
int ans;
void work () {
    int i , t;
    scanf ( "%d%d" , &n , &m );
    for ( i = 1 ; i <= n ; i++ ) {
        scanf ( "%d%d" , &x[i] , &y[i] );
        t = (m-1) / x[i] + 1;
        if ( i == 1 ) ans = t * y[i];
        else ans = min ( ans , t * y[i] );
    }
    printf ( "%d\n" , ans );
}
int main () {
    int t;
    scanf ( "%d" , &t );
    while ( t-- ) work ();
    return 0;
}