/*第一行一个整数 test(1 \le test \le 100)test(1≤test≤100) 表示数据组数。

对于每组数据，第一行两个整数 n, m(1 \le n \le 100, 1 \le m \le 10000)n,m(1≤n≤100,1≤m≤10000)。

接下来 nn 行，每行两个整数 x[i], y[i](1 \le x[i], y[i] \le 100)x[i],y[i](1≤x[i],y[i]≤100)。*/

#include <iostream>
#include <algorithm>
#include <cstring>
using namespace std;

long long int water[105],kaluli[105];
long long int n,m;

int main() {
    long long int T;cin>>T;
    for (long long int i = 1; i <= T; ++i) {
        cin>>n;cin>>m;

        for (long long int j = 1; j <= n; ++j) {
            cin>>water[j]>>kaluli[j];
        }

        long long int answer = 0x3fffffffffff;

        for (int j = 1; j <= n; ++j) {
            long long int beishu = m/water[j];
            long long int yushu = m%water[j];
            if(yushu==0)
            {
                answer = min(beishu*kaluli[j] , answer);
            }
            else{answer = min((beishu+1)*kaluli[j] , answer);}
        }

        cout<<answer<<endl;
    }
}