#include<bits/stdc++.h>
#define ll long long
#define ntr "\n"
#define mod (ll)(1e9+7)
#define taskname ""
#define frep freopen(taskname".inp","r",stdin); freopen(taskname".out","w",stdout);
using namespace std;
ll fenwick[2][100001];
ll sz[100001];
ll pos[100001];
ll depth[100001];
ll up[100001][20];
ll t;
ll n,m,q;
vector<ll> adj[100001];
struct edge{
ll u,v;
} edges[100001];
struct add{
ll p,w;
bool operator < (const add &other){
return w < other.w;
}
} add[100001];
struct query{
ll s,t,x,y,l,r,ans,numroad,lca;
} queries[100001];
vector<ll> sweep[100001];
void dfs(ll u=1,ll par=0){
up[u][0]=par;
for(int i=1;i<20;i++){
up[u][i]=up[up[u][i-1]][i-1];
}
depth[u]=depth[par]+1;
pos[u]=++t;
for(auto v:adj[u]){
if(v==par) continue;
dfs(v,u);
sz[u]+=sz[v];
}
sz[u]++;
}
ll lca(ll u,ll v){
if(depth[u]<depth[v]) swap(u,v);
ll k=depth[u]-depth[v];
for(int i=19;i>=0;i--){
if(k&(1<<i)) u=up[u][i];
}
if(u==v) return u;
for(int i=19;i>=0;i--){
if(up[u][i]!=up[v][i]){
u=up[u][i];
v=up[v][i];
}
}
return up[u][0];
}
void upd(ll u,ll val){
for(;u<=n;u+=u&-u){
if(val>0){
fenwick[0][u]+=val;
fenwick[1][u]++;
}
else{
fenwick[0][u]+=val;
fenwick[1][u]--;
}
}
}
ll get(ll u,ll type){
ll val=0;
for(;u>0;u-=u&-u){
val+=fenwick[type][u];
}
return val;
}
void proc(){
for(int i=1;i<=m;i++){
ll p=add[i].p,w=add[i].w;
upd(pos[edges[p].u],w);
upd(pos[edges[p].u]+sz[edges[p].u],-w);
for(auto po:sweep[i]){
auto &[u,v,x,y,l,r,ans,numroad,lc]=queries[po];
lc=lca(u,v);
ll val=get(pos[u],0)+get(pos[v],0)-2*get(pos[lc],0);
ll num=get(pos[u],1)+get(pos[v],1)-2*get(pos[lc],1);
if(val<=y){
if(x>=numroad-num){
ans=max(ans,x-(numroad-num));
}
l=i+1;
}
else{
r=i-1;
}
}
sweep[i]={};
}
for(int i=1;i<=n;i++){
fenwick[0][i]=fenwick[1][i]=0;
}
}
int main(){
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
//frep;
cin>>n>>m>>q;
for(int i=1;i<n;i++){
ll a,b;
cin>>a>>b;
adj[a].push_back(b);
adj[b].push_back(a);
edges[i]={a,b};
}
dfs();
for(int i=1;i<=n;i++){
ll &u=edges[i].u;
ll &v=edges[i].v;
if(depth[u]<depth[v]) swap(u,v);
}
for(int i=1;i<=m;i++){
ll p,w;
cin>>p>>w;
add[i]={p,w};
}
sort(add+1,add+m+1);
for(int i=1;i<=q;i++){
ll s,t,x,y;
cin>>s>>t>>x>>y;
queries[i]={s,t,x,y,1,m,-1,0,lca(s,t)};
}
for(int i=1;i<=m;i++){
ll u=edges[add[i].p].u;
upd(pos[u],add[i].w);
upd(pos[u]+sz[u],-add[i].w);
}
for(int i=1;i<=q;i++){
ll u=queries[i].s;
ll v=queries[i].t;
ll l=lca(u,v);
ll num=get(pos[u],1)+get(pos[v],1)-2*get(pos[l],1);
queries[i].numroad=num;
if(queries[i].x>=num) queries[i].ans=queries[i].x-num;
}
for(int i=1;i<=n;i++){
fenwick[0][i]=fenwick[1][i]=0;
}
while(true){
ll flag=1;
for(int i=1;i<=q;i++){
if(queries[i].r<queries[i].l) continue;
flag=0;
ll mid=(queries[i].l+queries[i].r)/2;
sweep[mid].push_back(i);
}
if(flag) break;
proc();
}
for(int i=1;i<=q;i++) cout<<queries[i].ans<<ntr;
}
