#include <cstdio>

using namespace std;

const int MOD = 1000000007;

int n , k , i , j , res;
int grad[310];

int main()
{
    freopen("colorare3.in","r",stdin);
    freopen("colorare3.out","w",stdout);

    scanf("%d %d", &n, &k);

    for (i = 1; i < n; ++i)
    {
        int x , y;
        scanf("%d %d", &x, &y);
        grad[x]++; grad[y]++;
    }

    res = 1;
    for (i = 1; i <= n; ++i)
        for (j = k - grad[i] + 1; j <= k - 1 * (i != 1); ++j)
            res = (1LL * res * j) % MOD;

    printf("%d\n", res);

    return 0;
}