#include <bits/stdc++.h>  // include all standard C++ libraries

using namespace std;

// Loops
#define _overload3(_1,_2,_3,name,...) name
#define _rep(i,n) repi(i,0,n)
#define repi(i,a,b) for(int i=int(a);i<int(b);++i)
#define _rrep(i,n) rrepi(i,n,0)
#define rrepi(i,a,b) for(int i=int(a)-1;i>=int(b);--i)

#define rep(...) _overload3(__VA_ARGS__,repi,_rep,)(__VA_ARGS__)
#define rrep(...) _overload3(__VA_ARGS__,rrepi,_rrep,)(__VA_ARGS__)
#define each(xi, x) for (auto&& xi : x)
// Note: we can use rep(i,N) or rep(i,from,to)


// typedef
using ll = long long;
template <class T> using vec = vector<T>;
using vi   = vector<int>;
using vvi  = vector<vi>;
using vvvi = vector<vvi>;
using pii  = pair<int, int>;


// Constants

// Shorter repr for frequently used terms
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define Fi first
#define Se second


// Algorithms
#define all(x) (x).begin(), (x).end()
#define uniq(v) v.erase( unique(all(v)), v.end() )
#define perm(c) sort(all(c));for(bool c##p=1;c##p;c##p=next_permutation(all(c)))

template<class T> pair<T, size_t> max(vector<T> &x){ auto it = max_element(all(x)); return mp(*it, it-x.begin()); }
template<class T> pair<T, size_t> min(vector<T> &x){ auto it = min_element(all(x)); return mp(*it, it-x.begin()); }

template<class T> inline bool chmax(T &maxval, const T &newval) { if (maxval<newval) { maxval=newval; return 1; } return 0; }
template<class T> inline bool chmin(T &minval, const T &newval) { if (minval>newval) { minval=newval; return 1; } return 0; }

// Utilities
// Grid world utilities
int dx[4]={0,1,0,-1};
int dy[4]={1,0,-1,0};
#define inside(H,W,y,x) 0<=(x) && (x)<(W) && 0<=(y) && (y)<(H)

inline int in() {int x; cin >> x; return x;} // read int from cin
inline  ll IN() {ll x; cin >> x; return x;}  // read ll from cin



// Debug
#ifdef LOCAL
  #include "dump.hpp"
  #define debug(x) cerr << #x << ": " << x << '\n'
#else
  #define dump(...)
  #define debug(x)
#endif


// Paste snippets here!!
template <int M>
struct ModInt {
    int num;
    ModInt(): num(0){ }
    ModInt(int num): num(num){ }
    operator int () const { return num; }
    template <class T> ModInt operator + (T n) const { auto ret = num + n; return ret >= M ? ret - M : ret; }
    template <class T> ModInt operator - (T n) const { auto ret = num - n; return ret < 0 ? ret + M : ret; }
    template <class T> ModInt operator * (T n) const { return (ll)num * n % M; }
    template <class T> ModInt operator / (T n) const { return (ll)num * modInv(ModInt(n)) % M; }
    template <class T> ModInt operator >> (T n) const { return num >> n; }
    template <class T> ModInt operator << (T n) const { return ((ll)num << n) % M; }
    template <class T> ModInt operator | (T n) const { return num | n; }
    template <class T> ModInt operator & (T n) const { return num & n; }
    template <class T> bool operator < (T n) const { return num < n; }
    template <class T> bool operator > (T n) const { return num > n; }
    template <class T> bool operator <= (T n) const { return num <= n; }
    template <class T> bool operator >= (T n) const { return num >= n; }
    template <class T> bool operator == (T n) const { return num == n; }
    template <class T> bool operator != (T n) const { return num != n; }
    ModInt operator ++ (int){ int ret = num; num = num == M + 1 ? 0 : num + 1; return ret; }
    ModInt operator -- (int){ int ret = num; num = num == 0 ? M - 1 : num - 1; return ret; }
    ModInt operator ++ (){ return num = num == M + 1 ? 0 : num + 1; }
    ModInt operator -- (){ return num = num == 0 ? M - 1 : num - 1; }
    template <class T> ModInt operator += (T n){ num += n; return num = num >= M ? num - M : num; }
    template <class T> ModInt operator -= (T n){ num -= n; return num = num < 0 ? num + M : num; }
    template <class T> ModInt operator *= (T n){ return num = (ll)num * n % M; }
    template <class T> ModInt operator /= (T n){ return num = (ll)num * modInv(n) % M; }
    template <class T> ModInt operator >>= (T n){ return num = num >> n; }
    template <class T> ModInt operator <<= (T n){ return num = ((ll)num << n) % M; }
    friend ModInt modPow(ModInt base, ModInt ex) {
        ModInt ret = 1;
        while(ex.num){
            if(ex.num & 1){ ret = ret * base; }
            ex >>= 1;
            base = base * base;
        }
        return ret;
    }
    static vector<ModInt> mFacts, mInvFacts;
    friend ModInt modFact(ModInt n){ return mFacts[n.num]; }        // 階乗: n! 
    friend ModInt modInvFact(ModInt n){ return mInvFacts[n.num]; }  // 階乗分の1: 1/n!
    friend ModInt modInv(ModInt n){ return modPow(n, M - 2); }      // 1/n
    friend ModInt modC(ModInt n, ModInt k){ return modFact(n) * modInvFact(k) * modInvFact(n - k); }  // nCk
    static void init(int n){
        mFacts.resize(n + 1);
        mInvFacts.resize(n + 1);
        mFacts[0] = 1;
        for(int i = 1; i <= n; i++){
            mFacts[i] = mFacts[i - 1] * i;
        }
        mInvFacts[n] = modInv(mFacts[n]);
        for(int i = n - 1; i >= 0; i--){
            mInvFacts[i] = mInvFacts[i + 1] * (i + 1);
        }
    }
    friend istream& operator >> (istream& in, ModInt& e){ return in >> e.num; }
    friend ostream& operator << (ostream& out, const ModInt& e) { return out << e.num; }
};

template <int M>
vector<ModInt<M>> ModInt<M>::mFacts;
template <int M>
vector<ModInt<M>> ModInt<M>::mInvFacts;
// using mint = ModInt<998244353>;
using mint = ModInt<1000000007>;

// 
mint choose(mint K, int D){
  // K色からD個選ぶ
  if(K<D) return 0;
  mint ret = 1;
  rep(i,(int)D){
    ret *= K;
    K--;
  }
  return ret;
}

mint dfs(vvi &G, int u, mint K, vector<bool> &visited){
  mint ret = 1;
  if(u==0) ret *= choose(K-1, G[0].size());
  else {
    ret *= choose(K-2, G[u].size()-1);
  }
  visited[u] = true;
  for(int v : G[u]){
    if(visited[v]) continue;
    ret *= dfs(G,v,K,visited);
  }
  return ret;
}
// 

int main(){
  cin.tie(0); ios::sync_with_stdio(false);    // Magic for faster cin
  int n, k; cin>>n>>k;
  int a, b;
  vvi G(n);
  vector<bool> visited(n,false);
  dump (n,k);
  rep(i,n-1){
    cin >> a >> b; a--; b--;
    if(a>b) swap(a,b);
    G[a].pb(b);
    G[b].pb(a);
  }
  mint ret = k;
  mint K = k;
  mint::init(k+5);
  ret *= dfs(G,0,K,visited);
  cout << ret << endl;
  return 0;
}


Measured memory_bytes: 10496