#include <bits/stdc++.h>
using namespace std;
#define all(x) x.begin(), x.end()
#define ar array
#define pb push_back
#define ln '\n'
#define int long long
using i64 = long long;
template <class F, class _S>
bool chmin(F &u, const _S &v){
bool flag = false;
if ( u > v ){
u = v; flag |= true;
}
return flag;
}
template <class F, class _S>
bool chmax(F &u, const _S &v){
bool flag = false;
if ( u < v ){
u = v; flag |= true;
}
return flag;
}
signed main(){
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m, q; cin >> n >> m >> q;
vector <vector<ar<int,2>>> G(n);
for ( int i = 0; i + 1 < n; i++ ){
int u, v; cin >> u >> v;
--u, --v;
G[u].pb({v, i});
G[v].pb({u, i});
}
vector <int> pt(n);
int cost = -1;
for ( int i = 0; i < m; i++ ){
int p, c; cin >> p >> c;
pt[--p]++;
cost = c;
}
vector <vector<int>> up(20, vector <int> (n)), sum(20, vector <int> (n));
vector <int> d(n), dp(n);
auto dfs = [&](auto dfs, int u, int p) -> void{
up[0][u] = p;
for ( int i = 1; i < 20; i++ ){
up[i][u] = up[i - 1][up[i - 1][u]];
}
for ( auto &[v, i]: G[u] ){
if ( v != p ){
d[v] = d[u] + 1;
dp[v] = dp[u] + pt[i];
dfs(dfs, v, u);
}
}
};
dfs(dfs, 0, 0);
auto lca = [&](int u, int v){
if ( d[u] < d[v] ) swap(u, v);
int df = d[u] - d[v];
for ( int i = 0; i < 20; i++ ){
if ( df >> i & 1 ){
u = up[i][u];
}
}
if ( u == v ){
return u;
}
for ( int i = 19; i >= 0; i-- ){
if ( up[i][u] != up[i][v] ){
u = up[i][u];
v = up[i][v];
}
}
return up[0][u];
};
auto get = [&](int u, int v){
return dp[u] + dp[v] - dp[lca(u, v)] * 2;
};
while ( q-- ){
int s, t, x, y;
cin >> s >> t >> x >> y;
--s, --t;
cout << max(-1LL, x - max(0LL, get(s, t) - y / cost)) << ln;
}
cout << '\n';
}
