//For higher stack size use g++ -O2 -std=c++11 -Wall -Wl,--stack=268435456 a.cpp -o a.exe in cmd
    #include <bits/stdc++.h>
    #include <cstdio>
    #include <cstring>
    #include <cmath>
    #include <cstring>
    #include <chrono>
    #include <complex>
    #define ll long long
    #define ld long double
    #define vi vector<int>
    #define vll vector<ll>
    #define vvi vector < vi >
    #define pii pair<int,int>
    #define pll pair<long long, long long>
    #define mod 1000000007
    #define inf 1000000000000000001;
    #define all(c) c.begin(),c.end()
    #define mp(x,y) make_pair(x,y)
    #define mem(a,val) memset(a,val,sizeof(a))
    #define eb emplace_back
    #define pb push_back
    #define f first
    #define s second

    using namespace std;
    int main()
    {
        std::ios::sync_with_stdio(false);
        int T;
        cin>>T;
        // cin.ignore(); must be there when using getline(cin, s)
        while(T--)
        {
            ll x,n,z,ans=2e18,i;
            cin>>n>>x;
            for(i=1;i<=n;++i)
            {
                cin>>z;
                z=z/__gcd(x,z);
                if (log10(x)+log10(z) > 18)
                    continue;
                ans=min(ans,x*z);
            }
            if(ans>1e18)
                ans=-1;
            cout<<ans<<endl;
        }
        return 0;
    }