#include <bits/stdc++.h>
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
#define REP(i, n) for (int i = 0; (i64)(i) < (i64)(n); ++i)

template <typename T>
using V = std::vector<T>;
template <typename T>
vector<T> make_vec(size_t n, T a) {
  return vector<T>(n, a);
}
template <typename... Ts>
auto make_vec(size_t n, Ts... ts) {
  return vector<decltype(make_vec(ts...))>(n, make_vec(ts...));
}
template <typename Container>
ostream &pprint(const Container &a, string_view sep = " ",
                string_view ends = "\n", ostream *os = nullptr) {
  if (os == nullptr) os = &cout;
  auto b = std::begin(a), e = std::end(a);
  for (auto it = std::begin(a); it != e; ++it) {
    if (it != b) *os << sep;
    *os << *it;
  }
  return *os << ends;
}
template <typename T>
ostream &operator<<(ostream &os, const vector<T> &a) {
  return pprint(a, ",", "", &(os << "[")) << "]";
}
template <typename T>
ostream &operator<<(ostream &os, const set<T> &a) {
  return pprint(a, ",", "", &(os << "{")) << "}";
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const map<T, U> &a) {
  return pprint(a, ", ", "", &(os << "{")) << "}";
}
template <typename T, typename U>
ostream &operator<<(ostream &os, const pair<T, U> &a) {
  return os << "(" << a.first << ", " << a.second << ")";
}

#ifdef ENABLE_DEBUG
template <typename T>
void debug(T value) {
  cerr << value;
}
template <typename T, typename... Ts>
void debug(T value, Ts... args) {
  cerr << value << ", ";
  debug(args...);
}
#define DEBUG(...)                              \
  do {                                          \
    cerr << " \033[33m (L" << __LINE__ << ") "; \
    cerr << #__VA_ARGS__ << ":\033[0m ";        \
    debug(__VA_ARGS__);                         \
    cerr << endl;                               \
  } while (0)
#else
#define debug(...)
#define DEBUG(...)
#endif

const i64 MOD = 1'000'000'007;

struct mint {
  long long x;
  mint(long long x = 0) : x((x % MOD + MOD) % MOD) {}
  mint operator-() const { return mint(-x); }
  mint &operator+=(const mint &a) {
    if ((x += a.x) >= MOD) x -= MOD;
    return *this;
  }
  mint &operator-=(const mint &a) {
    if ((x += MOD - a.x) >= MOD) x -= MOD;
    return *this;
  }
  mint &operator*=(const mint &a) {
    (x *= a.x) %= MOD;
    return *this;
  }
  mint pow(long long t) const {
    if (!t) return 1;
    mint a = pow(t >> 1);
    a *= a;
    if (t & 1) a *= *this;
    return a;
  }
  // for prime MOD
  mint inv() const { return pow(MOD - 2); }
  mint &operator/=(const mint &a) { return *this *= a.inv(); }
};
mint operator+(const mint &a, const mint &b) { return mint(a) += b; }
mint operator-(const mint &a, const mint &b) { return mint(a) -= b; }
mint operator*(const mint &a, const mint &b) { return mint(a) *= b; }
mint operator/(const mint &a, const mint &b) { return mint(a) /= b; }
bool operator==(const mint &a, const mint &b) { return a.x == b.x; }
bool operator!=(const mint &a, const mint &b) { return a.x != b.x; }
bool operator<(const mint &a, const mint &b) { return a.x < b.x; }
bool operator>(const mint &a, const mint &b) { return a.x > b.x; }
bool operator<=(const mint &a, const mint &b) { return a.x <= b.x; }
bool operator>=(const mint &a, const mint &b) { return a.x >= b.x; }
istream &operator>>(istream &is, mint &a) { return is >> a.x; }
ostream &operator<<(ostream &os, const mint &a) { return os << a.x; }

struct Factorials {
  // factorials and inverse factorials.
  vector<mint> fact, ifact;

  // n: max cached value.
  Factorials(int n) : fact(n + 1), ifact(n + 1) {
    assert(n < MOD);
    fact[0] = 1;
    for (int i = 1; i <= n; ++i) fact[i] = fact[i - 1] * i;
    ifact[n] = fact[n].inv();
    for (int i = n; i >= 1; --i) ifact[i - 1] = ifact[i] * i;
  }

  // Combination (nCk)
  mint C(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n] * ifact[k] * ifact[n - k];
  }

  // Permutation (nPk)
  mint P(int n, int k) {
    if (k < 0 || k > n) return 0;
    return fact[n] * ifact[n - k];
  }
};

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  int N, K;
  cin >> N >> K;
  V<V<int>> G(N);
  REP(i, N - 1) {
    int a, b;
    cin >> a >> b;
    a--;
    b--;
    G[a].push_back(b);
    G[b].push_back(a);
  }
  Factorials fs(100010);
  auto solve = [&](auto self, int v, int p) -> mint {
    int m = int(G[v].size()) - (p >= 0 ? 1 : 0);
    int n = K - (p >= 0 ? 2 : 1);
    if (n < 0) return 0;
    mint ans = fs.P(n, m);
    for (int u : G[v]) {
      if (u == p) continue;
      ans *= self(self, u, v);
    }
    return ans;
  };
  mint ans = solve(solve, 0, -1) * mint(K);
  cout << ans << endl;
}

Measured memory_bytes: 17008