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

const int cap = 2e6 + 5;
int t, n;
ll m, a[cap];
int idx, h[cap], nxt[cap * 2], to[cap * 2];

void add(int u, int v) {
    idx++;
    to[idx] = v;
    nxt[idx] = h[u];
    h[u] = idx;
}

int com(int u, int v) {
    ll dif = a[u] - a[v] + (u < v ? 1 : 0);
    if (m < dif) {
        return u;
    }
    ll rem = m - dif;
    if (rem % 2 == 0) {
        return v;
    }
    return u;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cin >> t;
    while (t--) {
        cin >> n >> m;
        int u = 1;
        for (int i = 1; i <= n; i++) {
            cin >> a[i];
            if (a[i] > a[u] || (a[i] == a[u] && i < u)) {
                u = i;
            }
        }
        idx = 0;
        for (int i = 1; i <= n; i++) {
            h[i] = 0;
        }
        for (int i = 1; i < n; i++) {
            int x, y;
            cin >> x >> y;
            add(x, y);
            add(y, x);
        }
        int v = 0;
        for (int i = h[u]; i; i = nxt[i]) {
            int w = to[i];
            if (v == 0 || a[w] > a[v] || (a[w] == a[v] && w < v)) {
                v = w;
            }
        }
        if (v == 0) {
            cout << u << '\n';
            continue;
        }
        cout << com(u, v) << '\n';
    }
    return 0;
}