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


using ll = long long;
using vi = vector<int>;
using vb = vector<bool>;
using vc = vector<char>;
using vs = vector<string>;
using vll = vector<ll>;

#define int long long
#define f first
#define s second
#define pb push_back
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define foo(i,a,b) for (int i = (a); i < (b); ++i)
#define rfoo(i,a,b) for (int i = (a); i >= (b); --i)
#define input(v) for (auto &x : v) cin >> x
#define print(v) for (auto x : v) cout << x << " "; cout << '\n'
#define yes cout << "YES" << std::endl;
#define no cout << "NO" << std::endl;
#define nl cout << "\n";


const int MOD = 1e9 + 7;
const ll INF = 1e18;

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }

ll power(ll a, ll b) {
    ll res = 1;
    while (b) {
        if (b & 1) res *= a;
        a *= a;
        b >>= 1;
    }
    return res;
}

ll modexp(ll a, ll b, ll mod = MOD) {
    ll res = 1;
    a %= mod;
    while (b) {
        if (b & 1) res = (res * a) % mod;
        a = (a * a) % mod;
        b >>= 1;
    }
    return res;
}

ll modmul(ll a, ll b, ll mod = MOD) {
    return ((a % mod) * (b % mod)) % mod;
}

bool isprime(int n) {
    if (n < 2) return false;
    for (int i = 2; i * i <= n; ++i)
        if (n % i == 0) return false;
    return true;
}

void sieve(int n, vector<bool> &isPrime) {
    isPrime.assign(n + 1, true);
    isPrime[0] = isPrime[1] = false;
    for (int i = 2; i * i <= n; ++i)
        if (isPrime[i])
            for (int j = i * i; j <= n; j += i)
                isPrime[j] = false;
}


int getbit(ll n, int b)      { return (n >> b) & 1; }
ll setbit(ll n, int b)       { return n | (1LL << b); }
ll resetbit(ll n, int b)     { return n & ~(1LL << b); }
ll togglebit(ll n, int b)    { return n ^ (1LL << b); }
bool ispoftwo(ll n)          { return n > 0 && !(n & (n - 1)); }
int countSetBits(ll n)       { return __builtin_popcountll(n); }

int digitCount(ll n, int base = 10) {
    return n ? (int)(log(n) / log(base)) + 1 : 1;
}

vi factors(int n) {
    vi res;
    for (int i = 1; i * i <= n; i++) {
        if (n % i == 0) {
            res.pb(i);
            if (i != n / i) res.pb(n / i);
        }
    }
    sort(all(res));
    return res;
}
#define lb(v, x) (lower_bound(all(v), x) - (v).begin())
#define ub(v, x) (upper_bound(all(v), x) - (v).begin())
#define count_occ(v, x) (ub(v, x) - lb(v, x))

#define fastio ios::sync_with_stdio(false); cin.tie(nullptr); cout.tie(nullptr)


signed main() {
    fastio;

    int t = 1;
    cin >> t;
    while (t--) 
    {
        int n,k; cin>>n>>k;

        vi v(n); input(v);
        int mini = INT_MAX;
        sort(all(v));
        v[0] -= k;
        int p =  1;
        foo(i,0,n) {
            p = p*v[i];
        }
        cout << p;
        // foo(i,0,n) {
        //     int p = 1;
        //     foo(j,0,n) {
        //         if (i == j) {
        //             p = p * (v[j]-k);
        //         }
        //         else {
        //             p = p * v[j];
        //         }
        //     }
        //     mini = min(p,mini);
        // }
        // cout<<mini;
        nl
    }

}