#include <bits/stdc++.h>
using namespace std;
const long long INF = (long long)1e18;
const int mod = (int)1e9 + 7;
const int MAXN = (int)4e5 + 5;
long long n, ans[MAXN], ext[MAXN];
vector<pair<int, pair<int, int>>> sorg[MAXN];
vector<pair<int, int>> adj[MAXN];
int a[MAXN];
const int L = 20;
int geri[MAXN];
int par[MAXN][L], dep[MAXN];
int tin[MAXN], tout[MAXN];
int Gt = 1;
void dfs0(int v, int pr) {
  tin[v] = Gt++;
  if (pr == -1) {
    dep[v] = 0;
    par[v][0] = v;
  } else {
    dep[v] = dep[pr] + 1;
    par[v][0] = pr;
  }
  for (int j = 1; j < L; j++) par[v][j] = par[par[v][j - 1]][j - 1];
  ext[v] = a[v];
  for (pair<int, int> j : adj[v]) {
    if (j.first == pr) continue;
    geri[j.first] = j.second;
    dfs0(j.first, v);
    ext[v] += max(0LL, -2LL * j.second + ext[j.first]);
  }
  tout[v] = Gt - 1;
}
int gtp(int v, int dd) {
  for (int i = L - 1; i >= 0; i--) {
    if ((1 << i) <= dd) {
      v = par[v][i];
      dd -= (1 << i);
    }
  }
  return v;
}
int find_lca(int a, int b) {
  if (dep[a] > dep[b]) swap(a, b);
  for (int i = L - 1; i >= 0; i--) {
    if (dep[a] + (1 << i) <= dep[b]) b = par[b][i];
  }
  if (a == b) return a;
  for (int i = L - 1; i >= 0; i--) {
    if (par[a][i] != par[b][i]) {
      a = par[a][i];
      b = par[b][i];
    }
  }
  return par[a][0];
}
long long t[MAXN];
void upd(int l, int r, long long val) {
  r++;
  for (; l < MAXN; l += (l & -l)) t[l] += val;
  for (; r < MAXN; r += (r & -r)) t[r] -= val;
}
long long gt(int v) {
  long long res = 0;
  for (; v; v -= (v & -v)) res += t[v];
  return res;
}
void dfs1(int v, int pr, long long sum) {
  upd(tin[v], tin[v], ext[v]);
  long long nS = sum + a[v];
  for (pair<int, int> u : adj[v]) {
    if (u.first == pr) continue;
    nS += max(0LL, -2 * u.second + ext[u.first]);
  }
  for (pair<int, int> u : adj[v]) {
    if (u.first == pr) continue;
    nS -= max(0LL, -2 * u.second + ext[u.first]);
    dfs1(u.first, v, max(0LL, nS - 2 * u.second));
    nS += max(0LL, -2 * u.second + ext[u.first]);
  }
  unordered_map<int, long long> mp;
  for (pair<int, int> u : adj[v]) {
    if (u.first == pr) continue;
    long long dg = max(0LL, -2 * u.second + ext[u.first]);
    mp[u.first] = dg;
  }
  for (auto u : sorg[v]) {
    int a = u.second.first, b = u.second.second;
    if (b == v) swap(a, b);
    if (a == v && b == v) {
      ans[u.first] = sum + ext[v];
    } else if (a == v) {
      int r1 = gtp(b, dep[b] - dep[v] - 1);
      ans[u.first] = sum + ext[v] + gt(tin[b]) - mp[r1] - geri[r1];
    } else {
      int r1 = gtp(b, dep[b] - dep[v] - 1), r2 = gtp(a, dep[a] - dep[v] - 1);
      ans[u.first] = sum + ext[v] + gt(tin[b]) + gt(tin[a]) - mp[r1] - mp[r2] -
                     geri[r1] - geri[r2];
    }
  }
  for (pair<int, int> u : adj[v]) {
    if (u.first == pr) continue;
    upd(tin[u.first], tout[u.first], ext[v] - mp[u.first] - u.second);
  }
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.tie(nullptr);
  int q;
  cin >> n >> q;
  for (int i = 1; i <= n; i++) cin >> a[i];
  for (int i = 0; i < n - 1; i++) {
    int u, v, w;
    cin >> u >> v >> w;
    adj[u].push_back({v, w});
    adj[v].push_back({u, w});
  }
  dfs0(1, -1);
  for (int i = 0; i < q; i++) {
    int u, v;
    cin >> u >> v;
    sorg[find_lca(u, v)].push_back({i, {u, v}});
  }
  dfs1(1, -1, 0);
  for (int i = 0; i < q; i++) cout << ans[i] << '\n';
}
