#include<algorithm>
#include<iostream>
#include<cstring>
#include<cstdio>
#include<vector>
#include<queue>
#include<set>
#include<map>
using namespace std;
typedef long long ll;
const int maxn = 2000 + 100;
const int mod = 1e9 + 7;
#define f(x) (x+x)

int main(){
    int t;
    scanf("%d", &t);
    while(t--){
        int n, m;
        scanf("%d%d", &n, &m);
        int ans = 99999999;
        for(int i = 0; i < n; ++i){
            int x, y;
            scanf("%d%d", &x, &y);
            ans = min(ans, (m-1)/x*y+y);
        }
        printf("%d\n", ans);
    }
    return 0;
}