#include <bits/stdc++.h>

using i64 = long long;
using u64 = unsigned long long;
using u32 = unsigned;

void solve() {
    int n;
    i64 k;
    std::cin >> n >> k;
    
    std::vector<i64> a(n);
    for (int i = 0; i < n; i++) {
        std::cin >> a[i];
    }
    
    auto get = [&](int i, i64 g) {
        std::vector<i64> pre(n + 1), suf(n + 1);
        for (int j = i; j < n; j++) {
            pre[j + 1] = std::gcd(pre[j], a[j] + k);
        }
        for (int j = n - 1; j >= i; j--) {
            suf[j] = std::gcd(suf[j + 1], a[j]);
        }
        i64 ans = 0;
        for (int j = i; j <= n; j++) {
            ans = std::max(ans, std::gcd(g, std::gcd(pre[j], suf[j])));
        }
        return ans;
    };
    
    i64 g = 0;
    i64 ans = 0;
    for (int i = 0; i < n; i++) {
        i64 ng = std::gcd(ng, a[i]);
        if (ng != g) {
            ans = std::max(ans, get(i, g));
        }
        g = ng;
    }
    ans = std::max(ans, g);
    std::cout << ans << "\n";
}

int main() {
    std::ios::sync_with_stdio(false);
    std::cin.tie(nullptr);
    
    int t;
    std::cin >> t;
    
    while (t--) {
        solve();
    }
    
    return 0;
}