#include <iostream>
#include <iomanip>

using namespace std;

double prec[101][10001];
    
int main()
{
    int T;
    cin >> T;
    cout << fixed << setprecision(15);
    
    prec[0][0] = 1;
    for (int i = 1; i <= 100; i++)
    {
        for (int j = 0; j <= (i - 1) * (i - 2) / 2; j++)
        {
            for (int k = 0; k < i; k++)
                prec[i][j + k] += prec[i - 1][j] / (i + 0.0);
        }
    }
    
    while (T)
    {
          T--;
          int n;
          long long k;
          cin >> n >> k;
          
          int a[200];
          
          for (int i = 0; i < n; i++) cin >> a[i];
                 
          int cnt = 0;
          
          for (int i = 0; i < n; i++)
          {
              for (int j = i + 1; j < n; j++)
              {
                  if (a[i] > a[j]) cnt++;
              }
          }
          if (k > n * (n - 1) / 2) cout << 0.0 << endl;
          else
          {
              double expected = 0;
              for (int j = 0; j <= (n - 1) * n / 2; j++)
              {
                  expected += j * prec[n][j];
              }
              
              int it = 0;              
              double sum = 0;
              double prob2 = 0;
              double prob = 1 - prec[n][0];
              
              int p = 1;
              
              //cout << expected << endl;
              
              for (int i = 1; i <= k; i++)
              {
                  while (it < n * (n - 1) / 2)
                  {
                        if (it + 1 - i > expected) break;
                        it++;
                        sum += it * prec[n][it];
                        prob -= prec[n][it];
                        prob2 += prec[n][it];
                  }
                  
                  while (it - i > expected)
                  {
                        sum -= it * prec[n][it];
                        prob += prec[n][it];
                        prob2 -= prec[n][it];
                        it--;
                  }

                  while ((p <= it) && (p <= i))                  
                  {
                        sum -= p * prec[n][p];
                        prob2 -= prec[n][p];
                        p++;
                  }
                  
                  if (i == k) break;
                  
                  expected = sum - i * prob2 + expected * prob;
                  
                  //cout << i << " " << it << " " << expected << endl;
              }
              
              if ((cnt <= it) || (!k)) cout << max(0 + 0.0, cnt - k + 0.0) << endl; 
              else cout << expected << endl;
          }
    }
//    system("pause");
    return 0;
}