#include <bits/stdc++.h>
using namespace std;
#define int long long
const int mod = 1e9 + 7, M = 61;
int dep[M], par[M];
vector<int> nei[M];
void dfs(int u)
{
for (int i:nei[u])
if (i!=par[u])
par[i]=u, dep[i]=dep[u]+1, dfs(i);
}
int lca(int u,int v)
{
if (dep[u]>dep[v]) swap(u,v);
while (dep[v]>dep[u]) v=par[v];
while (u!=v)
u=par[u], v=par[v];
return u;
}
signed main()
{
int n,m,k;
cin>>n>>m>>k;
int ans=1, pw[n];pw[0]=1;
for (int i=1;i<n;i++)
{
int u,v;
cin>>u>>v;
nei[u].push_back(v);
nei[v].push_back(u);
ans=ans*k%mod, pw[i]=ans;
}
dfs(1);
int msk[m]={};
for (int i=0;i<m;i++)
{
int u,v;
cin>>u>>v;
int p=lca(u,v);
while (u!=p)
msk[i]|=(1ll<<u), u=par[u];
while (v!=p)
msk[i]|=(1ll<<v), v=par[v];
}
for (int ms=1;ms<(1<<m);ms++)
{
int y=ms, uni=0, now=1;
while (y)
{
bool in=0;
for (int p=0;p<m;p++)
if (y>>p&1)
{
if (uni&msk[p]) uni|=msk[p], in=1, y-=(1<<p);
}
if (!in)
{
for (int p=0;p<m;p++)
if (y>>p&1)
{
uni|=msk[p], now=now*k%mod;
break;
}
}
}
int z=n-1-__builtin_popcountll(uni);
ans+=pw[z]*now%mod;
if (__builtin_popcount(ms)%2) ans-=2*pw[z]*now%mod;
ans=(ans+mod*2)%mod;
}
cout<<ans<<endl;
return 0;
}
