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

int n;
ll k,a[300005],pre[300005],suf[300005];

void sol()
{
    scanf("%d%lld",&n,&k);
    for(int i=1;i<=n;i++)
    {
        scanf("%lld",&a[i]);
        pre[i]=__gcd(pre[i-1],a[i]);
    }
    suf[n+1]=0;
    for(int i=n;i;i--) suf[i]=__gcd(suf[i+1],a[i]);
    ll ans=pre[n];
    for(int i=1;i<=n;i++)
    {
        if(pre[i]==pre[i-1]) continue;
        ll g=pre[i-1];
        for(int j=i;j<=n;j++)
        {
            g=__gcd(g,a[j])+k;
            ans=max(ans,__gcd(g,suf[j+1]));
        }
    }
    printf("%lld\n",ans);
}

int main()
{
	//freopen(".in","r",stdin);
	//freopen(".out","w",stdout);
	int t;
	scanf("%d",&t);
	while(t--) sol();
	return 0;
}