#include <bits/stdc++.h>
using namespace std;
const int N = 3e5 + 10;
long long int dp1[N], dp2[N], Sa[N], Sw[N], dp[20][N], A[N];
int P[20][N], H[N], n, q;
vector<pair<int, int> > adj[N];
void preDFS(int v, int p = -1) {
  if (!~p) P[0][v] = v;
  for (int i = 1; i < 20; i++) P[i][v] = P[i - 1][P[i - 1][v]];
  for (pair<int, int> u : adj[v]) {
    if (u.first != p) {
      P[0][u.first] = v;
      H[u.first] = H[v] + 1;
      Sw[u.first] = Sw[v] + u.second, Sa[u.first] = Sa[v] + A[u.first];
      preDFS(u.first, v);
    }
  }
}
int getpar(int v, int h) {
  for (int i = h; i; i -= i & -i) v = P[__builtin_ctz(i)][v];
  return v;
}
int LCA(int u, int v) {
  if (H[u] < H[v]) swap(u, v);
  u = getpar(u, H[u] - H[v]);
  if (u == v) return v;
  for (int i = 19; ~i; i--)
    if (P[i][u] != P[i][v]) u = P[i][u], v = P[i][v];
  return P[0][v];
}
void DFSdn(int v, int p = -1) {
  for (pair<int, int> u : adj[v]) {
    if (u.first != p)
      DFSdn(u.first, v),
          dp1[v] += max(0ll, dp1[u.first] - 2 * u.second + A[u.first]);
  }
}
void DFSup(int v, int p = -1) {
  for (pair<int, int> u : adj[v]) {
    if (u.first != p) {
      dp2[u.first] =
          max(0ll, A[v] + dp2[v] + dp1[v] -
                       max(0ll, dp1[u.first] - 2 * u.second + A[u.first]));
      dp2[u.first] = max(0ll, dp2[u.first] - 2 * u.second);
      DFSup(u.first, v);
    }
  }
}
void NIMA(int v, int p = -1) {
  for (pair<int, int> u : adj[v]) {
    if (u.first != p) {
      dp[0][u.first] =
          dp1[v] - max(0ll, dp1[u.first] - 2 * u.second + A[u.first]);
      NIMA(u.first, v);
    }
  }
}
long long int get(int v, int h) {
  long long int ret = 0;
  for (int i = h; i; i -= i & -i)
    ret += dp[__builtin_ctz(i)][v], v = P[__builtin_ctz(i)][v];
  return ret;
}
int main() {
  scanf("%d%d", &n, &q);
  for (int i = 1; i <= n; i++) scanf("%lld", &A[i]);
  for (int i = 1; i < n; i++) {
    int u, v, w;
    scanf("%d%d%d", &u, &v, &w);
    adj[u].push_back({v, w});
    adj[v].push_back({u, w});
  }
  preDFS(1);
  DFSdn(1);
  DFSup(1);
  NIMA(1);
  for (int i = 1; i < 20; i++)
    for (int j = 1; j <= n; j++)
      dp[i][j] = dp[i - 1][j] + dp[i - 1][P[i - 1][j]];
  for (; q; q--) {
    int u, v;
    scanf("%d%d", &u, &v);
    if (H[u] < H[v]) swap(u, v);
    if (u == v) {
      printf("%lld\n", dp1[u] + dp2[u] + A[u]);
      continue;
    }
    int p = LCA(u, v);
    long long int a = get(u, H[u] - H[p]), b = get(v, H[v] - H[p]);
    long long int ret =
        Sa[u] - Sa[p] + A[p] + Sa[v] - Sa[p] - (Sw[u] - Sw[p] + Sw[v] - Sw[p]);
    printf("%lld\n", a + b + dp2[p] - dp1[p] + ret + dp1[u] + dp1[v]);
  }
  return 0;
}
