#include <bits/stdc++.h>
#define INF 2000000000
#define MOD 1000000007
#define MAXN 200005
#define REP(temp, init_val, end_val) for (int temp = init_val; temp <= end_val; ++temp)
#define REPR(temp, init_val, end_val) for (int temp = init_val; temp >= end_val; --temp)
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> intpair;
int read(){
    int f = 1, x = 0;
    char c = getchar();
    while (c < '0' || c > '9'){if(c == '-') f = -f; c = getchar();}
    while (c >= '0' && c <= '9')x = x * 10 + c - '0', c = getchar();
    return f * x; 
}
inline int lowbit(int x){
    return x & (-x);
}
inline int modadd(int x, int y){
    return (x + y >= MOD ? x + y - MOD: x + y);
}
inline int sgn(int x){
    return (x < 0 ? -1: (x > 0 ? 1: 0));
}
template<typename T>
T gcd(T a, T b){
    return (!b) ? a: gcd(b, a % b);
}
int poww(int a, int b){
    int res = 1;
    while (b > 0){
        if (b & 1) res = 1ll * res * a % MOD;
        a = 1ll * a * a % MOD, b >>= 1;
    }
    return res;
}
const int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};
const int ddx[] = {-1, -1, -1, 0, 0, 1, 1, 1}, ddy[] = {-1, 0, 1, -1, 1, -1, 0, 1};

/*--------------------------------------------------------------------*/
/*--------------------------------------------------------------------*/

int n, m;
void init(){
    n = read(), m = read();
}
void solve(){
    int ans = 0x3f3f3f3f;
    REP(i, 1, n){
        int x = read(), y = read();
        int t = (m - 1) / x + 1;
        ans = min(ans, y * t);
    }
    printf("%d\n", ans);
}
int main(){
    int T = read();
    while (T--){
init();
    solve();
    }
    
    return 0;
}