class Combination
  #　組み合わせに必要な階乗、逆数、逆元の計算を初期化時に行って、のちの個別の計算を高速にする。
  def initialize(max_n, mod = 10 ** 9 + 7)
    @mod   = mod
    @max_n = max_n

    @fac  = Array.new(@max_n + 1) # 階乗
    @inv  = Array.new(@max_n + 1) # 逆数
    @finv = Array.new(@max_n + 1) # 逆元

    @fac[0]  = @fac[1] = 1
    @finv[0] = @finv[1] = 1
    @inv[1]  = 1
    2.upto(@max_n) do |i|
      @fac[i]  = @fac[i - 1] * i % @mod
      @inv[i]  = @mod - @inv[@mod % i] * (@mod / i) % @mod
      @finv[i] = @finv[i - 1] * @inv[i] % @mod
    end
  end

  def nCk(n, k)
    return 0 if (n < 0 || k < 0 || k > n)
    @fac[n] * @finv[n - k] * @finv[k] % @mod
  end

  def nPk(n, k)
    return 0 if (n < 0 || k < 0 || k > n)
    #@fac[n] * @finv[n - k] % @mod
    nCk(n, k) * @fac[k] % @mod
  end
end

$combination = Combination.new(1000000)

$n, $k = gets.chomp.split.map(&:to_i)
$edge  = Array.new($n).map { Array.new() }

($n - 1).times do
  a, b = gets.chomp.split.map(&:to_i).map(&:pred)
  $edge[a] << b;
  $edge[b] << a;
end


$ans    = 1
$MOD    = 10 ** 9 + 7
stack   = [0]
visited = [false] * $n

while (!stack.empty?)
  i          = stack.pop
  visited[i] = true
  if i == 0
    $ans = $combination.nPk($k, $edge[0].size + 1)
  else
    $ans *= $combination.nPk($k - 2, $edge[i].size - 1)
  end
  $ans %= $MOD
  $edge[i].each do |v|
    next if visited[v] == true
    stack << v
  end
end

puts $ans



