#include <bits/stdc++.h>
#define Nmax 100005
#define MOD 1000000007
#define pb push_back

using namespace std;

int dp[Nmax],f0[Nmax],f1[Nmax],n,k;
vector <int> L[Nmax];

inline void Dfs(int nod, int tata)
{
    int cnt=0;
    dp[nod]=1;
    for(auto it : L[nod])
        if(it!=tata)
        {
            Dfs(it,nod);
            dp[nod]=(1LL*dp[nod]*dp[it])%MOD;
            ++cnt;
        }

    if(tata) dp[nod]=(1LL*dp[nod]*f1[cnt])%MOD;
    else dp[nod]=(1LL*dp[nod]*f0[cnt])%MOD;
}

int main()
{
    int i,x,y;
    ifstream cin("colorare3.in");
    ofstream cout("colorare3.out");
    cin>>n>>k;

    for(i=f0[0]=1;i<=n;++i) f0[i]=(1LL*f0[i-1]*(k-i+1))%MOD;
    for(i=f1[0]=1;i<=n;++i) f1[i]=(1LL*f1[i-1]*(k-i))%MOD;

    for(i=1;i<n;++i)
    {
        cin>>x>>y;
        L[x].pb(y); L[y].pb(x);
    }
    Dfs(1,0);
    cout<<dp[1]<<"\n";
    return 0;
}