#include <bits/stdc++.h>
using namespace std;
#define task "main"
#define F first
#define S second
#define ii pair<int, int>
#define il pair<int, long long>
#define li pair<long long, int>
#define FOR(i, a, b) for(int i = (a); i <= (b); ++i)
#define FOD(i, b, a) for(int i = (b); i >= (a); --i)
template <class T1, class T2>
    bool maximize(T1 &a, T2 b){
        if (a < b) {a = b; return true;}
        return false;
    }
template <class T1, class T2>
    bool minimize(T1 &a, T2 b){
        if (a > b) {a = b; return true;}
        return false;
    }
template <class T>
    void printArr(T container, string separator = " ", string finish = "\n", ostream &out = cout){
        for(auto item: container) out << item << separator;
        out << finish;
    }
const int MAX_N = 65;
const int MOD = (int)1e9 + 7;
void add(int &x, int y) {
    x += y;
    if (x >= MOD) x -= MOD;
}
void sub(int &x, int y) {
    x -= y;
    if (x < 0) x += MOD;
}
int nNode, nPair, k;
vector<ii> adj[MAX_N];
ii magics[MAX_N];
int poww[MAX_N];
vector<int> path[MAX_N];
bool dfs(int u, int p, int dest, int id) {
    bool ok = (u == dest);
    for (ii e : adj[u]) {
        int v = e.F, edgeID = e.S;
        if (v == p) continue;
        if (dfs(v, u, dest, id)) {
            path[id].push_back(edgeID);
            ok = true;
        }
    }
    return ok;
}
int par[MAX_N], sz[MAX_N];
int nCom;
int getP(int a) {
    return (a == par[a] ? a : par[a] = getP(par[a]));
}
void unite(int u, int v) {
    u = getP(u), v = getP(v);
    if (u == v) return;
    nCom--;
    if (sz[u] < sz[v]) swap(u, v);
    par[v] = u;
    sz[u] += sz[v];
}
int calc(int mask) {
    FOR(i, 1, nNode - 1) par[i] = i, sz[i] = 1;
    nCom = nNode - 1;
    FOR(i, 0, nPair - 1) if (mask >> i & 1) {
        FOR(j, 0, (int)path[i + 1].size() - 2)
            unite(path[i + 1][j], path[i + 1][j + 1]);
    }
    return poww[nCom];
}
void solve() {
    cin >> nNode >> nPair >> k;
    FOR(i, 1, nNode - 1) {
        int u, v;
        cin >> u >> v;
        adj[u].push_back({v, i});
        adj[v].push_back({u, i});
    }
    FOR(i, 1, nPair) {
        cin >> magics[i].F >> magics[i].S;
        dfs(magics[i].F, -1, magics[i].S, i);
    }
    poww[0] = 1;
    FOR(i, 1, nNode) poww[i] = 1LL * poww[i - 1] * k % MOD;
    int ans = 0;
    FOR(mask, 0, (1 << nPair) - 1) {
        if (__builtin_popcount(mask) & 1)
            sub(ans, calc(mask));
        else
            add(ans, calc(mask));
    }
    cout << ans;
}
int32_t main() {
    if (fopen(task".inp", "r")) {
        freopen(task".inp", "r", stdin);
        freopen(task".out", "w", stdout);
    }
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    bool multitest = 0;
    int numTest = 1;
    if (multitest) cin >> numTest;
    while (numTest--) {
        solve();
    }
    return 0;
}
/* Lak lu theo dieu nhac!!!! */
Compilation message (stderr)
Main.cpp: In function 'int32_t main()':
Main.cpp:119:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  119 |         freopen(task".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Main.cpp:120:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  120 |         freopen(task".out", "w", stdout);
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