#include <bits/stdc++.h>
using namespace std;
const int MOD=1e9+7;
vector <int> v[61];
struct mazan
{
    int a,b,l;
} q[16];
int tata[61];
int nivel[61],smen[61],m;
bool marc[16];
bool viz[61];
unordered_map <long long,bool> harta;
bool leg[16][16];
int lca(int a,int b)
{
    if(nivel[a]>nivel[b])
        swap(a,b);
    while(nivel[b]>nivel[a])
        b=tata[b];
    while(a!=b)
    {
        a=tata[a];
        b=tata[b];
    }
    return a;
}
void dfs(int nod,int papa)
{
    tata[nod]=papa;
    nivel[nod]=nivel[papa]+1;
    for(auto it:v[nod])
        if(it!=papa)
            dfs(it,nod);
}
void dfsupd(int nod,int papa)
{
    for(auto it:v[nod])
        if(it!=papa)
        {
            dfsupd(it,nod);
            smen[nod]+=smen[it];
        }
}
int lgput(int a,int b)
{
    int rez=1;
    while(b)
    {
        if(b%2)
            rez=1LL*rez*a%MOD;
        a=1LL*a*a%MOD;
        b/=2;
    }
    return rez;
}
void dfsmuch(int a,int val)
{
    marc[a]=1;
    for(int i=0; i<m; i++)
        if(val&(1<<i)&&leg[a][i+1]&&!marc[i+1])
            dfsmuch(i+1,val);
}
bool dointersec(int a,int b,int c,int d)
{
    if(a==b||c==d)
        return 0;
    if(nivel[a]<=nivel[d]||nivel[c]<=nivel[b])
        return 0;
    int ca=a,cc=c;
    while(nivel[a]>nivel[d]+1)
        a=tata[a];
    while(nivel[c]>nivel[d]+1)
        c=tata[c];
    int ok=(a==c);
    a=ca;
    c=cc;
    while(nivel[a]>nivel[b]+1)
        a=tata[a];
    while(nivel[c]>nivel[b]+1)
        c=tata[c];
    ok&=(a==c);
    return ok;
}
int main()
{
#ifdef HOME
    freopen("test.in","r",stdin);
    freopen("test.out","w",stdout);
#endif
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);
    int n,i,a,b,k,j;
    cin>>n>>m>>k;
    for(i=1; i<n; i++)
    {
        cin>>a>>b;
        v[a].push_back(b);
        v[b].push_back(a);
    }
    dfs(1,0);
    for(i=1; i<=m; i++)
    {
        cin>>q[i].a>>q[i].b;
        q[i].l=lca(q[i].a,q[i].b);
    }
    for(i=1; i<=m; i++)
        for(j=i+1; j<=m; j++)
            leg[i][j]=leg[j][i]=(dointersec(q[i].a,q[i].l,q[j].a,q[j].l)|dointersec(q[i].a,q[i].l,q[j].b,q[j].l)|dointersec(q[i].b,q[i].l,q[j].b,q[j].l)|dointersec(q[i].b,q[i].l,q[j].a,q[j].l));
    int rez=lgput(k,n-1);
    for(i=1; i<(1<<m); i++)
    {
        int cnt=0,cate=0;
        for(j=1; j<=n; j++)
            smen[j]=0;
        for(j=1; j<=m; j++)
            marc[j]=0;
        for(j=0; j<m; j++)
            if(i&(1<<j))
            {
                cate++;
                smen[q[j+1].a]++;
                smen[q[j+1].b]++;
                smen[q[j+1].l]-=2;
            }
        int nrpart=0;
        for(j=0; j<m; j++)
            if(i&(1<<j)&&!marc[j+1])
            {
                dfsmuch(j+1,i);
                nrpart++;
            }
        dfsupd(1,0);
        for(j=1; j<=n; j++)
            if(smen[j])
                cnt++;
        if(cate%2)
            rez=(rez-lgput(k,n-1-cnt+nrpart)+MOD)%MOD;
        else
            rez=(rez+lgput(k,n-1-cnt+nrpart))%MOD;
    }
    cout<<rez;
    return 0;
}