#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;
const int MOD = (int)1e9 + 7;


//---------------------------------------------------------------
template<int MOD> struct ModInt { int x;
    explicit operator bool() const { return !!x; }
    ModInt(int v = 0) : x(v % MOD) { if (x < 0) x += MOD; }
    ModInt(long long v) : x(v % MOD) { if (x < 0) x += MOD; }
    ModInt &operator+=(const ModInt &r) { if ((x += r.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator-=(const ModInt &r) { if ((x += MOD - r.x) >= MOD) x -= MOD; return *this; }
    ModInt &operator*=(const ModInt &r) { x = 1LL * x * r.x % MOD; return *this; }
    ModInt &operator/=(const ModInt &r) { return *this *= r.inverse(); }
    ModInt operator-() const { return x ? ModInt(MOD - x) : ModInt(x); }
    ModInt operator+(const ModInt &r) const { return ModInt(*this) += r; }
    ModInt operator-(const ModInt &r) const { return ModInt(*this) -= r; }
    ModInt operator*(const ModInt &r) const { return ModInt(*this) *= r; }
    ModInt operator/(const ModInt &r) const { return ModInt(*this) /= r; }
    ModInt inverse() const { long long a = x, b = MOD, u = 1, v = 0;
        while (b) { long long t = a / b; a -= t * b; swap(a, b); u -= t * v; swap(u, v); }
        return ModInt(u); } // x.pow(MOD-2)
    ModInt pow(long long k) const { ModInt r(1), a(x);
        while (k) { if (k & 1) r *= a; a *= a; k >>= 1; } return r; }
    bool operator==(const ModInt r) const { return x == r.x; }
    bool operator!=(const ModInt r) const { return x != r.x; }
    bool operator< (const ModInt r) const { return x <  r.x; }
    friend ostream& operator<<(ostream &os, const ModInt<MOD>& a) { return os << a.x; }
    friend istream& operator>>(istream &is, ModInt<MOD>& a) { return is >> a.x; }
};
template<typename T, int SZ> struct Comb { vector<T> _fac, _ifac, _inv;
    Comb() : _fac(SZ + 1), _ifac(SZ + 1), _inv(SZ + 1) {
        _fac[0] = _ifac[SZ] = _inv[0] = 1;
        for (int i = 1; i <= SZ; i++) _fac[i] = _fac[i - 1] * i;
        _ifac[SZ] /= _fac[SZ];
        for (int i = SZ - 1; i >= 0; i--) _ifac[i] = _ifac[i + 1] * (i + 1);
        for (int i = 1; i <= SZ; i++) _inv[i] = _ifac[i] * _fac[i - 1]; }
    T inv(int n) { return n < 0 ? T(0) : _inv[n]; }
    T fac(int n) { return n < 0 ? T(0) : _fac[n]; }
    T ifac(int n) { return n < 0 ? T(0) : _ifac[n]; }
    T P(int a, int b) { return (b < 0 || a < b) ? T(0) : _fac[a] * _ifac[a - b]; }
    T C(int a, int b) { return b < 0 ? T(0) : P(a, b) * _ifac[b]; }
    T H(int n, int k) { if (n < 0 || k < 0) return T(0);
        return k == 0 ? T(0) : C(n + k - 1, k); }
};
typedef ModInt<MOD> mint;
//---------------------------------------------------------------

Comb<mint, 250000> com;
int k;
vector<vector<int>> g;
mint ans;
void dfs(int u, int p, bool is_root = false) {
    int chs = 0;
    for (int v: g[u]) if (v != p) {
        chs++;
        dfs(v, u);
    }
    if (is_root) ans *= com.P(k - 1, chs);
    else ans *= com.P(k - 2, chs);
}

int main() {
    int n; cin >> n >> k;
    g.resize(n);
    while (--n) {
        int a, b; cin >> a >> b; a--, b--;
        g[a].emplace_back(b);
        g[b].emplace_back(a);
    }
    ans = k;
    dfs(0, -1, true);
    cout << ans << endl;
    return 0;
}

Measured memory_bytes: 13312