#include<cstdio>
#define InFile "colorare3.in"
#define OutFile "colorare3.out"
#define MODULO 1000000007
#define NMAX 100001
using namespace std;
int N,x,y,v[NMAX];
long long K;
void citire(){
      scanf("%d%lld",&N,&K);
      int i;
      for(i=1;i<N;i++){
        scanf("%d%d",&x,&y);
        v[x]++;
        v[y]++;
      }
      fclose(stdin);
}
long long rezolvare(){
      int i,j,f=K;
      for(i=1;i<=N;i++){
        for(j=K-1;j>=K-v[i]+1;j--)
            f=(f*j)%MODULO;
      }
      return f;
}
int main(){
      freopen(InFile,"r",stdin);
      freopen(OutFile,"w",stdout);
      citire();
      printf("%lld",rezolvare());
      fclose(stdout);
      return 0;
}