#include <bits/stdc++.h>
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define bit(n) (1<<(n))
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef vector<int> vi;
typedef vector<ll> vl;
typedef vector<vi> vvi;
typedef vector<bool> vb;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
ll gcd(ll a, ll b) { return b?gcd(b,a%b):a;}
ll lcm(ll a, ll b) { return a/gcd(a,b)*b;}
int const INF = 1001001001;


// modint: mod 計算を int を扱うように扱える構造体
template<int MOD> struct Fp {
long long val;
constexpr Fp(long long v = 0) noexcept : val(v % MOD) {
if (val < 0) val += MOD;
}
constexpr int getmod() { return MOD; }
constexpr Fp operator - () const noexcept {
return val ? MOD - val : 0;
}
constexpr Fp operator + (const Fp& r) const noexcept { return Fp(*this) += r; }
constexpr Fp operator - (const Fp& r) const noexcept { return Fp(*this) -= r; }
constexpr Fp operator * (const Fp& r) const noexcept { return Fp(*this) *= r; }
constexpr Fp operator / (const Fp& r) const noexcept { return Fp(*this) /= r; }
constexpr Fp& operator += (const Fp& r) noexcept {
val += r.val;
if (val >= MOD) val -= MOD;
return *this;
}
constexpr Fp& operator -= (const Fp& r) noexcept {
val -= r.val;
if (val < 0) val += MOD;
return *this;
}
constexpr Fp& operator *= (const Fp& r) noexcept {
val = val * r.val % MOD;
return *this;
}
constexpr Fp& operator /= (const Fp& r) noexcept {
long long a = r.val, 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);
}
val = val * u % MOD;
if (val < 0) val += MOD;
return *this;
}
constexpr bool operator == (const Fp& r) const noexcept {
return this->val == r.val;
}
constexpr bool operator != (const Fp& r) const noexcept {
return this->val != r.val;
}
friend constexpr ostream& operator << (ostream &os, const Fp<MOD>& x) noexcept {
return os << x.val;
}
friend constexpr Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept {
if (n == 0) return 1;
auto t = modpow(a, n / 2);
t = t * t;
if (n & 1) t = t * a;
return t;
}
};

const int MOD = 1000000007;
using mint = Fp<MOD>;

vector<int> G[100010];
vector<bool> seen;
int N,K,M,s;
mint ans;

vector<mint> per(100050);

void dfs(int v) {
    seen[v] = true;
    if(v == s) {
        ans *= per[K-1] / per[K - 1 - M];
    }
    else {
        ans *= per[K-2] / per[K - 2 - SZ(G[v]) + 1];
    }
    for(auto nv : G[v]) {
        if(seen[nv]) continue;
        dfs(nv);
    }
}

int main() {
cin.tie(0);
ios::sync_with_stdio(false);

cin >> N >> K;
rep(i,N-1) {
    int a,b;
    cin >> a >> b;
    --a; --b;
    G[a].push_back(b);
    G[b].push_back(a);
}

M = 0;
rep(i,N) {
    if(chmax(M, SZ(G[i]))) s = i;
}

if(K <= M) {
    cout << 0 << endl;
    return 0;
}

per[0] = 1;
rrep(i,K) {
    per[i] = per[i-1] * i;
}

ans = K;
seen.assign(N, false);
dfs(s);

cout << ans << endl;
return 0;
}

Measured memory_bytes: 8832