#include <bits/stdc++.h>
using std::max;
const int N = 3e5 + 5;
template <typename T>
void read(T &x) {
  bool neg = false;
  unsigned char c = getchar();
  for (; (c ^ 48) > 9; c = getchar())
    if (c == '-') neg = true;
  for (x = 0; (c ^ 48) < 10; c = getchar()) x = (x << 3) + (x << 1) + (c ^ 48);
  if (neg) x = -x;
}
struct line {
  int next, to, w;
} e[2 * N];
int n, q, hd[N], cnt, a[N], b[N], fa[N], dep[N], siz[N], hc[N], top[N];
long long s[N], f[N], g[N], h[N], c[N], ff[N];
void adline(int u, int v, int w) {
  e[cnt].to = v;
  e[cnt].w = w;
  e[cnt].next = hd[u];
  hd[u] = cnt++;
}
void dfs1(int u) {
  hc[u] = -1;
  s[u] = s[fa[u]] + a[u] - b[u];
  for (int i = hd[u]; ~i; i = e[i].next) {
    int v = e[i].to;
    if (v == fa[u]) continue;
    fa[v] = u;
    b[v] = e[i].w;
    dep[v] = dep[u] + 1;
    dfs1(v);
    siz[u] += siz[v];
    if (!~hc[u] || siz[v] > siz[hc[u]]) hc[u] = v;
    f[u] += max(0ll, f[v] + a[v] - 2 * b[v]);
  }
  ++siz[u];
}
void dfs2(int u) {
  long long sum = (ff[u] = f[u]) + g[u] + a[u];
  h[u] = max(h[u], 0ll);
  if (~hc[u]) {
    int v = hc[u];
    top[v] = top[u];
    g[v] = max(0ll, sum - 2 * b[v] - max(0ll, h[v] = f[v] + a[v] - 2 * b[v]));
    dfs2(v);
  }
  for (int i = hd[u]; ~i; i = e[i].next) {
    int v = e[i].to;
    if (v == fa[u] || v == hc[u]) continue;
    g[v] = max(0ll, sum - 2 * b[v] - max(0ll, h[v] = f[v] + a[v] - 2 * b[v]));
    dfs2(top[v] = v);
  }
}
void dfs3(int u) {
  for (int i = hd[u]; ~i; i = e[i].next) {
    int v = e[i].to;
    if (v == fa[u]) continue;
    f[v] += f[u];
    h[v] += h[u];
    dfs3(v);
  }
}
int lca(int u, int v) {
  while (top[u] != top[v]) {
    if (dep[top[u]] > dep[top[v]])
      u = fa[top[u]];
    else
      v = fa[top[v]];
  }
  return dep[u] < dep[v] ? u : v;
}
int main() {
  read(n);
  read(q);
  for (int i = 0, i_end = n; i < i_end; ++i) read(a[i]);
  for (int i = 0, i_end = n; i < i_end; ++i) hd[i] = -1;
  for (int i = 0, i_end = n - 1; i < i_end; ++i) {
    int u, v, w;
    read(u);
    read(v);
    read(w);
    adline(--u, --v, w);
    adline(v, u, w);
  }
  dfs1(0);
  dfs2(0);
  dfs3(0);
  while (q--) {
    int u, v, m;
    long long ans;
    read(u);
    read(v);
    --u, --v;
    m = lca(u, v);
    ans = s[u] + s[v] - 2 * s[m] + a[m];
    ans += f[u] + f[v] - 2 * f[m] + g[m];
    ans -= h[u] + h[v] - 2 * h[m] - ff[m];
    printf("%lld\n", ans);
  }
  return 0;
}
