#include <iostream>
#include <vector>
using namespace std;
const int N = 70, mod = 1e9 + 7;
int hei[N], col[N], c[N], d[N], Par[N], final_Ans;
vector<int> nei[N];
void dfs(int u, int h){
hei[u] = h;
for (int i : nei[u]){
if (i == Par[u])
continue;
Par[i] = u;
dfs(i, h + 1);
}
}
int main(){
int n, m, k;
cin>>n>>m>>k;
for (int i=1;i<n;i++){
int a, b;
cin>>a>>b;
nei[a].push_back(b);
nei[b].push_back(a);
}
for (int j=0;j<m;j++)
cin>>c[j]>>d[j];
dfs(1, 1);
for (int mask = 0;mask < (1<<m);mask++){
for (int i=1;i<=n;i++)
col[i] = 0;
for (int j=0;j<m;j++){
if ((1<<j) & mask){
int u = c[j], v = d[j];
if (hei[u] > hei[v])
swap(u, v);
while (hei[v] > hei[u])
col[v] |= 1<<j, v = Par[v];
while (u != v)
col[v] |= 1<<j, col[u] |= 1<<j, u = Par[u], v = Par[v];
}
}
for (int l=1;l<=5;l++){
for (int i=1;i<=n;i++){
for (int j=1;j<=n;j++)
if (col[i] & col[j])
col[i] = col[j] = col[i] | col[j];
}
}
int msk = 0, Ans = 1;
for (int i=2;i<=n;i++){
if ((msk & col[i]) == 0)
Ans = 1LL * Ans * k % mod;
msk |= col[i];
}
if (__builtin_popcount(mask) % 2 == 1)
final_Ans = (final_Ans - Ans + mod) % mod;
else
final_Ans = (final_Ans + Ans) % mod;
}
cout<<final_Ans<<'\n';
}
