#include <bits/stdc++.h>
using namespace std;
#define mp make_pair
#define fi first
#define se second
#define all(x) x.begin(), x.end()
#define getbit(x, i) (((x) >> (i)) & 1)
#define bit(x) (1 << (x))
#define popcount __builtin_popcountll
mt19937_64 rd(chrono::steady_clock::now().time_since_epoch().count());
long long rand(long long l, long long r) {
return l + rd() % (r - l + 1);
}
const int N = 2e3 + 5;
const int mod = 1e9 + 7; // 998244353;
const int lg = 25; // lg + 1
const int inf = 1e9; // INT_MAX;
const long long llinf = 1e18; // LLONG_MAX;
template<class X, class Y>
bool minimize(X &a, Y b) {
return a > b ? (a = b, true) : false;
}
template<class X, class Y>
bool maximize(X &a, Y b) {
return a < b ? (a = b, true) : false;
}
template<class X, class Y>
bool add(X &a, Y b) {
a += b;
while (a >= mod) a -= mod;
while (a < 0) a += mod;
return true;
}
int n, k;
unordered_map<string, int> rec;
int c[N][N];
int f[N][N];
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
cin >> n >> k;
for (int i = 1; i <= n; ++i) {
string s;
cin >> s;
sort(all(s));
rec[s]++;
}
for (int i = 1; i <= n; ++i) {
c[0][i] = c[i][i] = 1;
for (int j = 1; j < i; ++j) {
add(c[j][i], c[j - 1][i - 1]);
add(c[j][i], c[j][i - 1]);
}
}
vector<int> words;
for (auto [s, i] : rec) words.push_back(i);
f[0][0] = 1;
for (int i = 1; i <= (int) words.size(); ++i) {
for (int cnt = 0; cnt <= words[i - 1]; ++cnt) {
for (int j = 0; j <= k; ++j) {
int offset = max(0, cnt * (cnt - 1) / 2);
if (j - offset >= 0) {
add(f[i][j], 1LL * c[cnt][words[i - 1]] * f[i - 1][j - offset] % mod);
}
}
}
}
cout << f[(int) words.size()][k];
return 0;
}
/*
*/
