#include<bits/stdc++.h>
using namespace std;
#define int long long
#define FOR(i,j,k) for(int i=j;i<=k;++i)
#define For(i,j,k) for(int i=j;i>=k;--i)
const int N = 2e5 + 111;
int a[N]; 
int son[N*60][2];
int d[65];
void sol(){
	int n,m;
	cin>>n>>m;
	FOR(i,1,n) cin>>a[i];
	int up = 60;
	
	FOR(i,0,up) d[i]=-1;
	
	int rt = 0;
	int cnt = 0;
	For(i,n,1){
		int now = rt;
		For(k,60,0){
			int val = 0;
			if(a[i]&(1ll<<k)) val = 1;
			if(son[now][val^1]){
				if(d[k]==-1){
					d[k] = val; 
				}
				else{
					if(d[k]!=val){
						return cout<<0<<'\n',void();
					}
				}
			}
			if(!son[now][val]) son[now][val] = ++cnt;
			now = son[now][val];
		}
	}
	int ans = 0;
	For(k,up,0){
		if(m&(1ll<<k)){
			if(d[k]==-1){
				int ccnt = 0;
				For(j,k-1,0) if(d[j]==-1) ++ccnt;
				ans += (1ll<<ccnt);
			}
			if(d[k]==0){
				int ccnt = 0;
				For(j,k-1,0) if(d[j]==-1) ++ccnt;
				ans += (1ll<<ccnt);
				break;
			}
		}
		else{
			if(d[k]==1){
				break;
			}
		}
	}
	FOR(i,0,cnt) son[i][0] = son[i][1] = 0;
	cout<<ans<<'\n';
}
signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	int t;
	cin>>t;
	while(t--){
		sol();
	}
	return 0;
}