#include <algorithm>
#include <cassert>
#include <cfloat>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstdlib>
#include <deque>
#include <iostream>
#include <iterator>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

#define FOR(i,k,n) for(int(i)=(k);(i)<(n);++(i))
#define rep(i,n) FOR(i,0,n)
#define all(v) begin(v),end(v)
#define debug(x) std::cerr<<#x<<": "<<x<<"\n"
#define debug2(x,y) std::cerr<<#x<<": "<<x<<", "<<#y<<": "<<y<<"\n"
#define debug3(x,y,z) std::cerr<<#x<<": "<<x<<", "<<#y<<": "<<y<<", "<<#z<<": "<<z<<"\n"

using ll=long long;
using vi=std::vector<int>;
using vvi=std::vector<vi>;
using vll=std::vector<ll>;
using vvll=std::vector<vll>;
template<typename T> using vvec=std::vector<std::vector<T>>;
template<typename T>
auto make_v(size_t sz){return std::vector<T>(sz);}
template<typename T,typename... Ts>
auto make_v(size_t sz,Ts...ts){return std::vector<decltype(make_v<T>(ts...))>(sz,make_v<T>(ts...));}
template<typename T>
void fill_v(T&var,const T&x){var=x;}
template<typename V,typename T>
void fill_v(V&v,const T&x){for(auto&& w:v){fill_v(w,x);}}

template<typename T> std::ostream& operator<<(std::ostream&s,const std::vector<T>&v){
  int sz=v.size();s<<"\n";rep(i,sz){s<<v[i];if(i<sz-1){s<<"\t";}}s<<"\n";return s;}
template<typename T> std::ostream& operator<<(std::ostream&s,const std::vector<std::vector<T>>&v){
  for(auto&& w:v){s<<w;}return s;}
template<typename T> std::ostream& operator<<(std::ostream&s,const std::deque<T>&v){
  int sz=v.size();s<<"\n";rep(i,sz){s<<v[i];if(i<sz-1){s<<"\t";}}s<<"\n";return s;}
template<typename T> std::ostream& operator<<(std::ostream&s,const std::deque<std::deque<T>>&v){
  for(auto&& w:v){s<<w;}return s;}
template<typename T> std::ostream& operator<<(std::ostream&s, const std::set<T>&v){
  s<<"\n";for(auto&& elm:v){s<<elm<<"\t";}s<<"\n";return s;}

inline void scan(int&a){scanf("%d",&a);}
inline void scan(ll&a){scanf("%lld",&a);}
inline void scan(char&a){scanf(" %c",&a);}
inline void scan(double&a){scanf("%lf",&a);}
inline void scan(std::string&s){char BUF[3000000];scanf(" %s",BUF);s=std::string(BUF);}
template<typename T>
inline void scan(std::vector<T>&v){for(auto&& sv:v){scan(sv);}}
template<typename First,typename...Args>
inline void scan(First&f,Args&...args){scan(f);scan(args...);}
inline void print(int a){printf("%d\n",a);}
inline void print(ll a){printf("%lld\n",a);}
inline void print(double a){printf("%.12f\n",a);}
inline void print(std::string s){std::cout<<s<<"\n";}

using namespace std;

class PermComb {
public:
  int mod;
  int sz;
  vll fact;
  vll frev;

  PermComb(int mod, int sz) : mod(mod), sz(sz), fact(sz+1), frev(sz+1) {
    fact[0] = 1;
    for (int i = 0; i < sz; ++i) {
      fact[i+1] = fact[i] * (i+1) % mod;
    }

    rep (i, sz+1) {
      frev[i] = po(fact[i], mod-2);
    }
  }

  ll po(ll k, ll x) {
    ll ret = 1;
    while (x) {
      if (x & 1) {
        ret = ret * k % mod;
      }
      k = k * k % mod;
      x >>= 1;
    }
    return ret;
  }

  ll perm(int n, int k) {
    assert (sz >= n && sz >= k);
    if (n < 0 || k < 0 || n < k) {
      return 0;
    }
    return fact[n] * frev[n-k] % mod;
  }

  ll comb(int n, int k) {
    assert (sz >= n && sz >= k);
    if (n < 0 || k < 0 || n < k) {
      return 0;
    }
    return fact[n] * frev[n-k] % mod * frev[k] % mod;
  }
};

int mod = 1000000007;

void calculate(vvi& g, vi& parent, vvi& children) {
  deque<int> que = {0};
  while (!que.empty()) {
    int u = que.front();
    que.pop_front();
    for (int v : g[u]) {
      if (v == parent[u]) {
        continue;
      }
      children[u].push_back(v);
      parent[v] = u;
      que.push_back(v);
    }
  }
}

int main() {
  int n, k;
  scan(n, k);
  vvi g(n);
  rep (i, n-1) {
    int a, b;
    scan(a, b);
    --a; --b;
    g[a].push_back(b);
    g[b].push_back(a);
  }
  vi parent(n, -1);
  vvi children(n);
  calculate(g, parent, children);

  auto pc = PermComb(mod, 100000);
  ll ans = pc.perm(k, (int)children[0].size() + 1);
  deque<int> que;
  for (int u : children[0]) {
    que.push_back(u);
  }
  while (!que.empty()) {
    int u = que.front();
    que.pop_front();
    ans = ans * pc.perm(k-2, (int)children[u].size()) % mod;
    for (int v : children[u]) {
      que.push_back(v);
    }
  }
  print(ans);

  return 0;
}


Measured memory_bytes: 13184