#include<stdio.h>

int main()
{
    int t;
    scanf("%d", &t);
    for (int r = 0; r < t; r++) {
        int n, m;
        int min = 1000000000;
        scanf("%d%d", &n, &m);
        for (int i = 0; i < n; i++) {
            int x, y;
            scanf("%d%d", &x, &y);
            int w = 0;
            if (m % x == 0) {
                w = (m / x) * y;
            }
            else {
                w = (m / x + 1) * y;
            }
            if (w < min) {
                min = w;
            }
        }
        printf("%d\n", min);
    }
    return 0;
}