/*
[templates]: 
duipai
spjdp
compre
addhis
floor_sum
treedfs
matrix
network_flow
polynomial
lca
bitset
valuesgt
fenwick
erbitree
*/
//#pragma GCC optimize("Ofast")
//#pragma GCC target("avx")
#include<bits/stdc++.h>
using namespace std;
#define int long long
//use ll instead of int.
#define f(i, a, b) for(int i = (a); i <= (b); i++)
#define cl(i, n) i.clear(),i.resize(n);
#define endl '\n'
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
const int inf = 1e18;
//#define cerr if(false)cerr
//#define freopen if(false)freopen
mt19937 rng(time(0)); 
int rnd(int l, int r) {return rng() % (r-l+1) + l; }
#define watch(x) cerr  << (#x) << ' '<<'i'<<'s'<<' ' << x << endl
void pofe(int number, int bitnum) {
    string s; f(i, 0, bitnum) {s += char(number & 1) + '0'; number >>= 1; } 
    reverse(s.begin(), s.end()); cerr << s << endl; 
    return;
}
template <typename TYP> void cmax(TYP &x, TYP y) {if(x < y) x = y;}
template <typename TYP> void cmin(TYP &x, TYP y) {if(x > y) x = y;}
//调不出来给我对拍！
//use std::array.
const int N = 200000; vector<int> t[N + 10]; int a[N + 10]; 
int anc[22][N + 10], dep[N + 10]; 
struct qj {
    int mx, mn, ans; 
}node[22][N + 10], e; 
qj merge(qj x, qj y) {
    return {max(x.mx, y.mx), min(x.mn, y.mn), max({x.ans, y.ans, y.mx - x.mn})}; 
}
// void print(qj x) {
    // cerr << "mn = " << x.mn << ", mx = " << x.mx << ", ans = " << x.ans << endl; 
// }
void dfs(int now, int fa) {
    anc[0][now] = fa; node[0][now] = {a[now], a[now], 0}; dep[now] = dep[fa] + 1; 
    for(int i = 1; i <= __lg(dep[now]); i ++) {
        anc[i][now] = anc[i - 1][anc[i - 1][now]]; 
        node[i][now] = merge(node[i - 1][now], node[i - 1][anc[i - 1][now]]); 
        // cerr << "node[" << i << "][" << now << "]: \n"; 
        // print(node[i][now]); 
    }
    for(int i : t[now]) {
        if(i != fa) {
            dfs(i, now); 
        }
    }
}
qj getmin(int now, int k) {
    qj res = e; 
    int c = 0; 
    while(k) {
        if(k & 1) {
            res = merge(res, node[c][now]); now = anc[c][now]; 
        }
        c ++; 
        k >>= 1; 
    }
    // cerr << res.ans << " " << res.mx << " " << res.mn << endl; 
    // cerr << "min = " << res << endl; 
    return res; 
}
signed main() {
    ios::sync_with_stdio(0);
    cin.tie(NULL);
    cout.tie(NULL);
    //freopen();
    //freopen();
    //time_t start = clock();
    //think twice,code once.
    //think once,debug forever.
    int n, q; cin >> n >> q; e.mx = -inf, e.mn = inf, e.ans = 0; 
    f(i, 1, n - 1) {
        int u, v; cin >> u >> v; 
        t[u].push_back(v); t[v].push_back(u); 
    }
    f(i, 1, n) cin >> a[i]; 
    dfs(1, 0);
    f(i, 1, q) {
        int l, r; cin >> l >> r; 
        int k = dep[l] - dep[r] + 1; 
        // cerr << k << endl; 
        cout << getmin(l, k).ans << endl; 
    }
    //time_t finish = clock();
    //cout << "time used:" << (finish-start) * 1.0 / CLOCKS_PER_SEC <<"s"<< endl;
    return 0;
}