#include <bits/stdc++.h>
using namespace std;
const int mod = 1e9 + 7;
const int MAX = 100;
struct mint{
int v;
mint() : v(0) {}
mint(int v) : v(v) {}
mint& operator += (const mint& o){ v += o.v; if(v >= mod) v -= mod; return *this; }
mint& operator -= (const mint& o){ v -= o.v; if(v < 0) v += mod; return *this; }
mint& operator *= (const mint& o){ v = 1ll * v * o.v % mod; return *this; }
friend mint operator + (mint a, const mint& b){ return a += b; }
friend mint operator - (mint a, const mint& b){ return a -= b; }
friend mint operator * (mint a, const mint& b){ return a *= b; }
};
int N, M, K, depth[MAX], par[MAX];
vector<int> adj[MAX], paths[MAX];
mint pw_k[MAX];
void dfs(int u, int p){
for(auto v : adj[u]) if(v != p){
par[v] = u;
depth[v] = depth[u] + 1;
dfs(v, u);
}
}
vector<int> get_path(int u, int v){ //exclude lca(u, v)
vector<int> vt;
while(depth[u] > depth[v]) vt.push_back(u), u = par[u];
while(depth[u] < depth[v]) vt.push_back(v), v = par[v];
while(u != v){
vt.push_back(u);
vt.push_back(v);
u = par[u]; v = par[v];
}
return vt;
}
int lab[MAX];
int root(int u){
return lab[u] < 0 ? u : (lab[u] = root(lab[u]));
}
int cnt;
bool join(int u, int v){
u = root(u);
v = root(v);
if(u == v) return false;
if(lab[u] > lab[v]) swap(u, v);
lab[u] += lab[v];
lab[v] = u;
--cnt;
return true;
}
int main(){
ios_base::sync_with_stdio(0); cin.tie(0);
cin >> N >> M >> K;
for(int i = 0; i + 1 < N; ++i){
int u, v;
cin >> u >> v;
--u, --v;
adj[u].emplace_back(v);
adj[v].emplace_back(u);
}
dfs(0, -1);
for(int i = 0; i < M; ++i){
int u, v;
cin >> u >> v;
--u, --v;
paths[i] = get_path(u, v);
}
pw_k[0] = 1;
for(int i = 1; i <= N; ++i) pw_k[i] = pw_k[i - 1] * mint(K);
mint all_combinations = pw_k[N - 1];
mint inv = 0;
for(int mask = 1; mask < (1 << M); ++mask){
fill(lab + 1, lab + N, -1);
cnt=N-1;
for(int i = 0; i < M; ++i)
if(mask >> i & 1)
for(int j=1;j<paths[i].size();++j)
join(paths[i][j-1],paths[i][j]);
int cnt_same = cnt;
if(__builtin_parity(mask)) inv += pw_k[cnt_same];
else inv -= pw_k[cnt_same];
}
mint ans = all_combinations - inv;
cout << ans.v << '\n';
return 0;
}
