#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 5;
const int mod = 1e9 + 7;
int n, q, u, v, w;
int a[N];
vector<pair<int, int> > adj[N];
long long dpU[N], dpD[N];
int tb[19][N], lvl[N];
long long sv1[N], sv2[N], sv3[N];
void dfs0(int u, int p) {
  tb[0][u] = p;
  for (int i = 1; i < 19; i++) tb[i][u] = tb[i - 1][tb[i - 1][u]];
  for (auto v : adj[u])
    if (v.first != p) {
      lvl[v.first] = lvl[u] + 1;
      dfs0(v.first, u);
    }
}
int LCA(int u, int v) {
  int d = lvl[v] - lvl[u];
  for (int i = 0; i < 19; i++)
    if (d >> i & 1) v = tb[i][v];
  if (u == v) return u;
  for (int i = 18; i >= 0; i--)
    if (tb[i][v] != tb[i][u]) v = tb[i][v], u = tb[i][u];
  return tb[0][u];
}
void dfs1(int u, int p) {
  dpD[u] = a[u];
  for (auto v : adj[u])
    if (v.first != p) {
      dfs1(v.first, u);
      dpD[u] += max(0ll, dpD[v.first] - 2 * v.second);
    }
}
void dfs2(int u, int p) {
  for (auto v : adj[u])
    if (v.first != p) {
      dpU[v.first] =
          max(0ll, +dpU[u] + dpD[u] - max(0ll, dpD[v.first] - 2 * v.second) -
                       2 * v.second);
      dfs2(v.first, u);
    }
}
void dfs3(int u, int p) {
  for (auto v : adj[u])
    if (v.first != p) {
      sv2[v.first] = sv2[u] - v.second;
      sv3[v.first] = sv3[u] + (dpD[u] - max(0ll, dpD[v.first] - 2 * v.second));
      dfs3(v.first, u);
    }
}
long long getExeclusion(int from, int to) {
  swap(from, to);
  long long ret = sv2[to] - sv2[from];
  ret += sv3[to] - sv3[from];
  return ret;
}
int main() {
  scanf("%d%d", &n, &q);
  for (int i = 1; i < n + 1; i++) scanf("%d", a + i);
  for (int i = 1; i < n; i++) {
    scanf("%d%d%d", &u, &v, &w);
    adj[u].push_back(pair<int, int>(v, w));
    adj[v].push_back(pair<int, int>(u, w));
  }
  dfs0(1, 0);
  dfs1(1, 0);
  dfs2(1, 0);
  dfs3(1, 0);
  for (int i = 0; i < q; i++) {
    scanf("%d%d", &u, &v);
    if (lvl[u] > lvl[v]) swap(u, v);
    if (LCA(u, v) == u)
      printf("%lld\n", dpU[u] + dpD[v] + getExeclusion(v, u));
    else
      printf("%lld\n", dpU[LCA(u, v)] + dpD[u] + dpD[v] +
                           getExeclusion(u, LCA(u, v)) +
                           getExeclusion(v, LCA(u, v)) - dpD[LCA(u, v)]);
  }
  return 0;
}
