#include <bits/stdc++.h>
using namespace std;
const int dx[4] = {1,0,-1,0}, dy[4] = {0,1,0,-1};
#define OVL(x,s) for(auto y:x) cout<<y<<s; cout<<"\n";
#ifdef IOI
void dbg_out() { cout << endl; }
template<typename Head, typename... Tail> void dbg_out(Head H, Tail... T) { cout << ' ' << H; dbg_out(T...); }
#define dbg(...) cout << "(" << #__VA_ARGS__ << "):", dbg_out(__VA_ARGS__);
#else
#define dbg(...) 1337;
#endif
#define endl "\n"
#define pb push_back
#define F first
#define S second
#define ll long long
#define mod 1000000007
#define all(v) v.begin(),v.end()
#define int long long
const int MAXN=2e5+100;
const int LOGN=21;
vector<int> v[MAXN];
int depth[MAXN];
vector<int> c[MAXN];
int up[MAXN][LOGN+1];
vector<pair<int,int>> edges;
map<pair<int,int>,int> mp;
int p[MAXN];
int ff[MAXN];
void dfs(int node,int par){
depth[node]=depth[par]+1;
up[node][0]=par;
p[node]=par;
ff[node]=ff[par]+c[mp[{node,par}]].size();
for(int i=1;i<LOGN;i++){
up[node][i]=up[up[node][i-1]][i-1];
}
for(auto x:v[node]){
if(x==par) continue;
dfs(x,node);
}
}
int LCA(int a,int b){
if(depth[a]<depth[b]) swap(a,b);
int d=depth[a]-depth[b];
for(int i=LOGN-1;i>=0;i--){
if((1<<i)&d){
a=up[a][i];
}
}
if(a==b) return a;
for(int i=LOGN-1;i>=0;i--){
if(up[a][i]!=up[b][i]){
a=up[a][i];
b=up[b][i];
}
}
return up[a][0];
}
signed main(){
ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
int n,m,q;
cin>>n>>m>>q;
for(int i=0;i<n-1;i++){
int a,b;
cin>>a>>b;
v[a].pb(b);
v[b].pb(a);
edges.pb({a,b});
mp[{a,b}]=mp[{b,a}]=i;
}
int c1=0;
for(int i=0;i<m;i++){
int t;
int d;
cin>>t>>d;
t--;
c1=d;
int a=edges[t].F;
int b=edges[t].S;
c[t].pb(d);
}
for(int i=0;i<n;i++){
sort(all(c[i]));
}
dfs(1,1);
while(q--){
int a,b,x,y;
cin>>a>>b>>x>>y;
int l=LCA(a,b);
int k=ff[a]+ff[b]-2*ff[l];
y/=c1;
vector<int> d;
while(a!=l){
int t=p[a];
for(auto x:c[mp[{a,t}]]) d.pb(x);
a=p[a];
}
while(b!=l){
int t=p[b];
for(auto x:c[mp[{b,t}]]) d.pb(x);
b=p[b];
}
// dbg(d.size(),k)
assert((d.size())==k);
// sort(all(d));
int f=k-y;
if(x>=f){
cout<<x-f<<endl;
continue;
}else cout<<-1<<endl;
}
}
