#include <bits/stdc++.h>

#define MaxN 100005
#define INF 2140000000
#define MOD 1000000007
using namespace std;

FILE *IN,*OUT;

int N,K,fr[MaxN],X,Y,ans;
int Arrangements(int n,int k)
{
    int aux=1;
    if(k>n)
        return 0;
    for(int i=n;i>n-k;i--)
        aux=1LL*aux*i%MOD;
    return aux;
}
int main()
{
    IN=fopen("colorare3.in","r");
    OUT=fopen("colorare3.out","w");

    fscanf(IN,"%d%d",&N,&K);

    for(int i=1;i<N;i++)
    {
        fscanf(IN,"%d%d",&X,&Y);
        fr[X]++,fr[Y]++;
    }

    ans=Arrangements(K,fr[1]);

    for(int i=2;i<=N;i++)
        ans=1LL*ans*Arrangements(K-1,fr[i]-1)%MOD;

    fprintf(OUT,"%d",ans);

    return 0;
}