#include <bits/stdc++.h>

using namespace std;
using ll = long long;
#define endl '\n'

void oper(int testcase_i) {
    ll n, k;
    cin >> n >> k;

    vector<ll> a(n + 1), a_k(n + 1);
    vector<ll> prpr(n + 2);
    for (int i = 1; i <= n; i++) {
        cin >> a[i];
        a_k[i] = a[i] + k;
        prpr[i] = __gcd(prpr[i - 1], a[i]);
    }

    vector<ll> ne(n + 10);
    ne[n] = a[n];
    for (int i = n - 1; i >= 1; i--) {
        ne[i] = __gcd(ne[i + 1], a[i]);
    }

    ll ans = 1;
    ll prgcdx = 0;
    for (int l = 0; l <= n; l++) {
        ll gcdx = __gcd(prgcdx, a[l]);
        if (gcdx == prpr[l + 1]) {
            continue;
        }
        prgcdx = gcdx;
        
        ll gcdrnow = 0;
        for (int r = l + 1; r <= n; r++) {
            gcdrnow = __gcd(gcdrnow, a_k[r]);
            ans = max(ans, __gcd(gcdx, __gcd(gcdrnow, ne[r + 1])));
        }
    }
    cout << ans << endl;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr), cout.tie(nullptr);
    int ttt = 1;
    cin >> ttt;
    for (int i = 1; i <= ttt; i++) {
        oper(i);
    }
    return 0;
}