import java.io.BufferedInputStream;
import java.util.*;

/**
 * @author hum
 */
public class Main {

    public static void main(String[] args) {
        Scanner sc = new Scanner(new BufferedInputStream(System.in));
        int t = sc.nextInt();
        for (int cas = 1; cas <= t; cas++) {
            int n = sc.nextInt();
            int m = sc.nextInt();
            int result = (int) 1e5;
            while (n-- > 0) {
                int a = sc.nextInt();
                int b = sc.nextInt();
                int tmp = m / a;
                if (m % a != 0) {
                    tmp++;
                }
                result = Math.min(result, tmp * b);
            }
            System.out.println(result);
        }
    }
}