//Nguyen Huu Hoang Minh
#include <bits/stdc++.h>
#define sz(x) int(x.size())
#define all(x) x.begin(),x.end()
#define reset(x) memset(x, 0,sizeof(x))
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define N 100005
#define remain(x) if (x > MOD) x -= MOD
#define ii pair<int, int>
#define iii pair<ii, int>
#define iiii pair< ii , ii >
#define viiii vector< iiii >
#define vi vector<int>
#define vii vector< ii >
#define bit(x, i) (((x) >> (i)) & 1)
#define Task "test"
#define int long long

using namespace std;

typedef long double ld;
const int inf = 1e10;
const int minf = -1e10;

int n,m,q;
vector<int> g[N];
int d[N], par[N][20], f[N];
int ic[N];

void readfile()
{
    ios_base::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    if (fopen(Task".inp","r"))
    {
        freopen(Task".inp","r",stdin);
        //freopen(Task".out","w",stdout);
    }
    cin >> n >> m >> q;
    for(int i=1; i<n; i++){
        int u, v;
        cin >> u >> v;
        g[u].pb(v);
        g[v].pb(u);
    }
}

void dfs(int u, int pre){
    for(int i=1; i<20; i++){
        par[u][i] = par[par[u][i-1]][i-1];
    }
    for(auto v : g[u]){
        if (v!=pre){
            d[v] = d[u]+1;
            par[v][0] = u;
            dfs(v,u);
        }
    }
}

int lca(int u, int v){
    if (d[u] < d[v]) swap(u,v);
    int delta = d[u]-d[v];
    for(int i=19; i>=0; i--){
        if (bit(delta,i)) u = par[u][i];
    }
    if (u==v) return u;
    for(int i=19; i>=0; i--){
        if (par[u][i]!=par[v][i]){
            u = par[u][i];
            v = par[v][i];
        }
    }
    return par[u][0];
}

int vst[N];

void dfs1(int u, int pre){
    for(auto v : g[u]){
        if (v!=pre){
            dfs1(v,u);
            f[u] += f[v];
        }
    }
}

void dfs2(int u, int pre){
    for(auto v : g[u]){
        if (v!=pre){
            f[v] += f[u];
            dfs2(v,u);
        }
    }
}

void proc()
{
    par[1][0] = 0;
    dfs(1,1);
    memset(f, 0, sizeof f);
    for(int i=1; i<=m; i++){
        int u, v, w;
        cin >> u >> v >> w;
        int z = lca(u,v);
        f[u]+=w;
        f[v]+=w;
        f[z]-=w;
        f[par[z][0]]-=w;
    }
    dfs1(1,1);
    dfs2(1,1);
    f[0] = 0;
    while (q--){
        int u, v;
        cin >> u >> v;
        int z = lca(u,v);
        cout << f[u]+f[v]-f[z]-f[par[z][0]] << '\n';
    }
}

signed main()
{
    readfile();
    proc();
    return 0;
}