#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N = 1e5 + 1 , LOG = 22;
int n , m , q , e = 0;
vector<int> LCA(N) , t(N) , D(N) , o(N) , U(N) , V(N) , ans(N) , L(N) , R(N) , P(N) , C(N) , S(N) , T(N) , X(N) , Y(N) , in(N) , out(N) , d(N);
vector<vector<int>> g(N) , up(N , vector<int>(LOG));
vector<int> order = {0};
void upd(int u , int x){
while(u <= n){
t[u] += x;
o[u] += (x > 0 ? 1 : -1);
u += u&-u;
}
}
int GET(int u){
int sum = 0;
while(u > 0){
sum += t[u];
u -= u&-u;
}
return sum;
}
int get(int u){
int sum = 0;
while(u > 0){
sum += o[u];
u -= u&-u;
}
return sum;
}
void dfs(int u , int p = 1){
in[u] = ++e;
up[u][0] = p;
d[u] = d[p] + 1;
for(int x = 0;x < (int)g[u].size();x ++){
if(g[u][x] != p){
dfs(g[u][x] , u);
}
}
out[u] = e;
}
void DFS(int u , int p = 1){
D[u] += D[p];
for(int x = 0;x < (int)g[u].size();x ++){
if(g[u][x] != p){
DFS(g[u][x] , u);
}
}
}
int lca(int u , int v){
if(d[u] < d[v]){
swap(u , v);
}
int s = d[u] - d[v];
for(int bit = 0;bit < LOG;bit ++){
if(s >> bit & 1){
u = up[u][bit];
}
}
if(u == v){
return u;
}
for(int bit = LOG - 1;bit >= 0;bit --){
if(up[u][bit] != up[v][bit]){
u = up[u][bit];
v = up[v][bit];
}
}
return up[u][0];
}
main(){
cin >> n >> m >> q;
for(int i = 1;i < n;i ++){
cin >> U[i] >> V[i];
g[U[i]].push_back(V[i]);
g[V[i]].push_back(U[i]);
}
for(int i = 1;i <= m;i ++){
cin >> P[i] >> C[i];
}
for(int i = 1;i <= q;i ++){
cin >> S[i] >> T[i] >> X[i] >> Y[i];
L[i] = 1 , R[i] = m;
ans[i] = -1;
}
dfs(1);
for(int i = 1;i <= m;i ++){
if(d[U[i]] < d[V[i]]){
swap(U[i] , V[i]);
}
++D[U[i]];
}
DFS(1);
for(int bit = 1;bit < LOG;bit ++){
for(int u = 1;u <= n;u ++){
up[u][bit] = up[up[u][bit - 1]][bit - 1];
}
}
for(int i = 1;i <= q;i ++){
LCA[i] = lca(S[i] , T[i]);
ans[i] = X[i] - (D[S[i]] + D[T[i]] - 2 * D[LCA[i]]);
}
for(int i = 1;i <= m;i ++){
order.push_back(i);
}
sort(order.begin() + 1 , order.end() , [&](int x , int y){
return C[x] < C[y];
});
int E = 1;
while(E){
E = 0;
vector<int>(n + 1).swap(t);
vector<int>(n + 1).swap(o);
vector<vector<int>> query(n + 1);
for(int i = 1;i <= q;i ++){
if(L[i] <= R[i]){
query[(L[i] + R[i]) / 2].push_back(i);
E = 1;
}
}
for(int x = 1;x <= m;x ++){
int v = P[order[x]];
upd(in[v] , C[order[x]]);
upd(out[v] + 1 , -C[order[x]]);
for(int id : query[x]){
int cost_silver = GET(in[S[id]]) + GET(in[T[id]]) - 2 * GET(in[LCA[id]]);
int h = get(in[S[id]]) + get(in[T[id]]) - 2 * get(in[LCA[id]]);
if(cost_silver <= Y[id]){
ans[id] = X[id] - (D[S[id]] + D[T[id]] - 2 * D[LCA[id]] - h);
L[id] = x + 1;
}else{
R[id] = x - 1;
}
}
}
}
for(int i = 1;i <= q;i ++){
cout << max(ans[i] , -1LL) << endl;
}
}
