#include <bits/stdc++.h>
#include<ext/pb_ds/hash_policy.hpp>
#include<ext/pb_ds/assoc_container.hpp>
using namespace __gnu_pbds;
using namespace std;
typedef long long LL;
typedef unsigned long long uLL;
struct custom_hash {
       static uint64_t splitmix64(uint64_t x) {
           x += 0x9e3779b97f4a7c15;
        x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
        x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
        return x ^ (x >> 31);
    }
    size_t operator()(uint64_t x) const {
        static const uint64_t FIXED_RANDOM = chrono::steady_clock::now().time_since_epoch().count();
        return splitmix64(x + FIXED_RANDOM);
    }
};
LL z = 1;
int read(){
    int x, f = 1;
    char ch;
    while(ch = getchar(), ch < '0' || ch > '9') if(ch == '-') f = -1;
    x = ch - '0';
    while(ch = getchar(), ch >= '0' && ch <= '9') x = x * 10 + ch - 48;
    return x * f;
}
int ksm(int a, int b, int p){
    int s = 1;
    while(b){
        if(b & 1) s = z * s * a % p;
        a = z * a * a % p;
        b >>= 1;
    }
    return s;
}
int main(){
    int i, j, x, y, n, m, T, ans;
    T = read();
    while(T--){
        ans = 1e9;
        n = read(); m = read();
        for(i = 1; i <= n; i++){
            x = read(); y = read();
            int t = (m - 1) / x + 1;
            ans = min(ans, t * y);
        }
        printf("%d\n", ans);
    }
    return 0;
}