#include <bits/stdc++.h>
#define int long long
struct Node
{
int stop;
int was;
Node(int stop, int was) : stop(stop), was(was) {};
Node() = default;
};
const int MAXN = 1e5 + 1;
const int LOGN = 20;
int up[MAXN][LOGN];
int dp[MAXN][LOGN];
int h[MAXN];
void dfs(int v, std::vector<std::vector<Node>> &g, int pred = -1)
{
if (pred == -1)
{
h[v] = 0;
}
else
{
h[v] = h[pred] + 1;
}
for (int i = 1; i < LOGN; i++)
{
up[v][i] = up[up[v][i - 1]][i - 1];
dp[v][i] = dp[up[v][i - 1]][i - 1] + dp[v][i - 1];
}
for (auto u : g[v])
{
if (u.stop != pred)
{
up[u.stop][0] = v;
dp[u.stop][0] = u.was;
dfs(u.stop, g, v);
}
}
}
int LCA(int a, int b)
{
if (h[a] > h[b])
{
std::swap(a, b);
}
int ans = 0;
for (int i = LOGN - 1; i >= 0; i--)
{
if ((h[b] - h[a]) >= (1 << i))
{
ans += dp[b][i];
b = up[b][i];
}
}
// std::cout << a << ' ' << b << "djfs;l" << std::endl;
if (a == b)
{
return ans;
}
for (int i = LOGN - 1; i >= 0; i--)
{
if (up[a][i] != up[b][i])
{
ans += dp[a][i];
ans += dp[b][i];
a = up[a][i];
b = up[b][i];
}
}
ans += dp[a][0];
ans += dp[b][0];
return ans;
}
signed
main()
{
int n, m, q;
std::cin >> n >> m >> q;
std::vector<std::pair<int, int>> all(n - 1);
for (int i = 0; i < n - 1; i++)
{
std::cin >> all[i].first >> all[i].second;
all[i].first--, all[i].second--;
}
std::vector<int> is_bad(n - 1, 0);
int cost = 0;
for (int i = 0; i < m; i++)
{
int p, c;
std::cin >> p >> c;
cost = c;
is_bad[--p]++;
}
std::vector<std::vector<Node>> g(n);
for (int i = 0; i < n - 1; i++)
{
g[all[i].first].push_back(Node(all[i].second, is_bad[i]));
g[all[i].second].push_back(Node(all[i].first, is_bad[i]));
}
up[0][0] = 0;
dfs(0, g);
while (q--)
{
int start, stop, x, y;
std::cin >> start >> stop >> x >> y;
start--, stop--;
int cnt = LCA(start, stop);
int can_take = y / cost;
if (can_take >= cnt)
{
std::cout << x << std::endl;
continue;
}
int delta = cnt - can_take;
if (delta > x)
{
std::cout << -1 << std::endl;
}
else
{
std::cout << x - delta << std::endl;
}
}
}
