#include <bits/stdc++.h> 
using namespace std;

#define inf 5e14+5
#define ll unsigned long long
struct Node {
	ll x, y;
}b[300005];
ll n, k, t, a[300005], ans;
void check(ll num)
{
	if (num <= 10)
		return;
	ll x, y, cnt = 0;
	x = num / 10, y = num % 10, cnt++;
	while (x>0)
	{
		if ((ll)(num / pow(10, cnt)) % 10 == 0) {
			cnt++;
			continue;
		}
		if (x <= n && y <= a[x]) {
			b[++ans].x = x;
			b[ans].y = y;
		}
		cnt++;
		x = num / (ll)pow(10, cnt);
		y = num % (ll)pow(10, cnt);
	}
}
bool cmp(Node x,Node y) {
	if (x.x != y.x)
		return x.x < y.x;
	return x.y < y.y;
}
void solve() {
	ll s = k;
	while (1)
	{
		if (s > inf)
			break;
		check(s);
		s *= k;
	}
	sort(b + 1, b + 1 + ans,cmp);
	cout << ans << endl;
	for (int i = 1; i <= ans; i++)
		cout << b[i].x << " " << b[i].y << endl;
}
int main() {
	cin >> t;
	while (t--)
	{
		ans = 0;
		cin >> n >> k;
		for (int i = 1; i <= n; i++)
			cin >> a[i];
		if (k == 1) {
			cout << ans << endl;
			continue;
		}
		solve();
	}
	return 0;
}