#include <stdio.h>

#define MAXN 100007
#define INF 1e9

int n, m, t;
int x[MAXN], y[MAXN];

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

  return 0;
}