#include <bits/stdc++.h>
using namespace std;
#pragma warning(disable : 4996)
struct Edge {
  int to, w;
};
const int N = 3e5 + 5, L = 20;
vector<Edge> v[N];
int a[N], tin[N], tout[N], p[N][L];
long long maxPath[N], maxUpPath[N], sum[N], pt[N], ancw[N];
int timer = 0;
bool upper(int a, int b) { return tin[a] <= tin[b] && tout[a] >= tout[b]; }
int getBeforeLca(int a, int b) {
  if (upper(a, b)) return -1;
  for (int i = L - 1; i >= 0; i--) {
    if (!upper(p[a][i], b)) a = p[a][i];
  }
  return a;
}
void dfs(int node, int anc) {
  p[node][0] = anc;
  for (int i = 1; i < L; i++) {
    p[node][i] = p[p[node][i - 1]][i - 1];
  }
  tin[node] = timer++;
  sum[node] = maxPath[node] = a[node];
  for (auto e : v[node]) {
    if (e.to != anc) {
      ancw[e.to] = e.w;
      dfs(e.to, node);
      maxPath[e.to] = max(0ll, maxPath[e.to] - e.w * 2);
      maxPath[node] += maxPath[e.to];
      sum[node] += maxPath[e.to];
    }
  }
  tout[node] = timer;
}
void deep(int node, long long x, long long y, int anc) {
  maxUpPath[node] = x - y;
  x += sum[node];
  for (auto e : v[node]) {
    if (e.to != anc) {
      pt[e.to] = pt[node] - e.w + sum[node] - maxPath[e.to];
      long long nx = x - e.w * 2 - maxPath[e.to];
      deep(e.to, nx, min(y, nx), node);
    }
  }
}
signed main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  int n, q;
  cin >> n >> q;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  for (int i = 0; i < n - 1; i++) {
    int a, b, w;
    cin >> a >> b >> w;
    a--, b--;
    v[a].push_back({b, w});
    v[b].push_back({a, w});
  }
  dfs(0, 0);
  deep(0, 0, 0, -1);
  for (int i = 0; i < q; i++) {
    int x, y, xx, yy, lca;
    cin >> x >> y;
    x--, y--;
    xx = getBeforeLca(x, y);
    yy = getBeforeLca(y, x);
    lca = xx == -1 ? x : p[xx][0];
    long long ans = maxUpPath[lca] + sum[lca];
    if (x != lca) {
      ans += sum[x] - maxPath[xx] + pt[x] - pt[xx] - ancw[xx];
    }
    if (y != lca) {
      ans += sum[y] - maxPath[yy] + pt[y] - pt[yy] - ancw[yy];
    }
    cout << ans << "\n";
  }
  return 0;
}
