#include <bits/stdc++.h>
template<typename T>
class fixed_point : T {
  public:
    explicit constexpr fixed_point (T&& t) noexcept
      : T(std::forward<T>(t)) {}
    template<typename... Args>
    constexpr decltype(auto) operator()(Args&&... args) const
      {return T::operator()(*this, std::forward<Args>(args)...);}
};
template<typename T>
static inline constexpr decltype(auto) fix (T&& t) noexcept {
  return fixed_point<T>{std::forward<T>(t)};
}
template <typename T>
T inverse(T a, T m) {
  T u = 0, v = 1;
  while (a != 0) {
    T t = m / a;
    m -= t * a; std::swap(a, m);
    u -= t * v; std::swap(u, v);
  }
  assert(m == 1);
  return u;
}
template <typename T>
class modular {
  private:
    int value;
  public:
    constexpr modular() = default;
    constexpr modular(const modular&) = default;
    constexpr modular(modular&&) = default;
    modular& operator=(const modular&) = default;
    modular& operator=(modular&&) = default;

    template <typename U>
    modular (const U& x) {value = normalize(x);}

    template <typename U>
    static auto normalize(const U& x) {
      int v = static_cast<int>(-mod() <= x && x < mod() ? x : x % mod());
      if (v < 0) v += mod();
      return v;
    }

    auto const& operator()() const { return value; }
    template <typename U>
    explicit operator U() const { return static_cast<U>(value); }
    constexpr static auto mod() { return T::value; }

    auto& operator+=(const modular& other) {
      if ((value += other.value) >= mod()) value -= mod();
      return *this;
    }
    auto& operator-=(const modular& other) {
      if ((value -= other.value) < 0) value += mod();
      return *this;
    }
    template <typename U>
    auto& operator+=(const U& other) {return *this += modular(other); }
    template <typename U>
    auto& operator-=(const U& other) {return *this -= modular(other); }
    auto operator-() const { return modular(-value); }

    template <typename U = T>
    auto& operator*=(const modular& rhs) {
      value = normalize(static_cast<int64_t>(value) * static_cast<int64_t>(rhs.value));
      return *this;
    }
    auto& operator/=(const modular& other) {
      return *this *= modular(inverse(other.value, mod()));
    }
};

template <typename T> bool operator==(const modular<T>& lhs, const modular<T>& rhs) { return lhs.value == rhs.value; }
template <typename T, typename U> bool operator==(const modular<T>& lhs, U rhs) { return lhs == modular<T>(rhs); }
template <typename T, typename U> bool operator==(U lhs, const modular<T>& rhs) { return modular<T>(lhs) == rhs; }

template <typename T> bool operator!=(const modular<T>& lhs, const modular<T>& rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(const modular<T>& lhs, U rhs) { return !(lhs == rhs); }
template <typename T, typename U> bool operator!=(U lhs, const modular<T>& rhs) { return !(lhs == rhs); }

template <typename T> modular<T> operator+(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) += rhs; }
template <typename T, typename U> modular<T> operator+(const modular<T>& lhs, U rhs) { return modular<T>(lhs) += rhs; }
template <typename T, typename U> modular<T> operator+(U lhs, const modular<T>& rhs) { return modular<T>(lhs) += rhs; }

template <typename T> modular<T> operator-(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) -= rhs; }
template <typename T, typename U> modular<T> operator-(const modular<T>& lhs, U rhs) { return modular<T>(lhs) -= rhs; }
template <typename T, typename U> modular<T> operator-(U lhs, const modular<T>& rhs) { return modular<T>(lhs) -= rhs; }

template <typename T> modular<T> operator*(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) *= rhs; }
template <typename T, typename U> modular<T> operator*(const modular<T>& lhs, U rhs) { return modular<T>(lhs) *= rhs; }
template <typename T, typename U> modular<T> operator*(U lhs, const modular<T>& rhs) { return modular<T>(lhs) *= rhs; }

template <typename T> modular<T> operator/(const modular<T>& lhs, const modular<T>& rhs) { return modular<T>(lhs) /= rhs; }
template <typename T, typename U> modular<T> operator/(const modular<T>& lhs, U rhs) { return modular<T>(lhs) /= rhs; }
template <typename T, typename U> modular<T> operator/(U lhs, const modular<T>& rhs) { return modular<T>(lhs) /= rhs; }

template<typename T, typename U>
modular<T> pow (const modular<T>& a, U b) {
  assert(b >= 0);
  modular<T> x = a, ret = 1;
  for (; b > 0; b /= 2) {
    if (b % 2 == 1) ret *= x;
    x *= x;
  }
  return ret;
}

template <typename T>
std::string to_string(const modular<T>& a) {
  return std::to_string(a());
}
template <typename T>
std::ostream& operator<<(std::ostream& stream, const modular<T>& a) {
  return stream << a();
}
template <typename T>
std::istream& operator>>(std::istream& stream, modular<T>& a) {
  int x; stream >> x;
  a.value = modular<T>::normalize(x);
  return stream;
}
constexpr int md = 1'000'000'007;
using mint = modular<std::integral_constant<std::decay_t<decltype(md)>, md>>;
#define LOCAL
using std::to_string;
auto to_string(std::string s) -> std::string {
  return '"' + s + '"';
}
auto to_string(const char* s) -> std::string {
  return to_string((std::string) s);
}
auto to_string(bool b) -> std::string {
  return (b ? "true" : "false");
}
template <typename T, typename U>
auto to_string(std::pair<T, U> p) -> std::string {
  return "(" + to_string(p.first) + ", " + to_string(p.second) + ")";
}
template <typename T>
auto to_string(T v) -> std::string {
  bool flg = false;
  std::string res = "{";
  for (auto const&x : v) {
    if (flg) res += ", ";
    else flg = true;
    res += to_string(x);
  }
  res += "}";
  return res;
}
void debug_out() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  std::cerr << " " << to_string(H);
  debug_out(T...);
}
#ifdef LOCAL
#define debug(...) std::cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...) 42
#endif
int main() {
  std::cin.tie(0); std::cin.sync_with_stdio(false);
  int n, k; std::cin >> n >> k;
  std::vector<std::vector<int>> grh(n);
  auto insert = [&] (int i, int j) {
    grh.at(i).push_back(j);
    grh.at(j).push_back(i);
  };
  for (int i = 0; i < n - 1; i++) {
    int u, v; std::cin >> u >> v;
    insert(--u, --v);
  }
  int mx = std::max(n, k) * 2;
  std::vector<mint> fct(mx, 1);
  for (int i = 1; i < mx; i++) {
    fct.at(i) = fct.at(i - 1) * i;
  }
  auto choose = [&] (int cal, int cld) {
    if (cal < cld) return mint(0);
    return fct.at(cal) / fct.at(cal - cld);
  };
  mint ret = k;
  fix ([&](auto dfs, int crr, int prt) -> void {
    int deg = grh.at(crr).size();
    mint tmp = 1;
    if (crr == prt) {
      tmp = choose(k - 1, deg);
    } else {
      tmp = choose(k - 2, deg - 1);
    }
    ret *= tmp;
    for (auto const& nxt : grh[crr]) if (nxt != prt) {
      dfs(nxt, crr);
    }
  })(0, 0);
  std::cout << ret << std::endl;
  return 0;
}

Measured memory_bytes: 12416