E

#include <bits/stdc++.h>

using namespace std;

#define ll     long long
#define pb     push_back

int main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);
    cout.tie(NULL);

    ll int a[105][105], p[105], cost[105];
    double dp[105];
    int n, m;

    cin>>n>>m;
    fill(dp, dp+105, -1);

    for(int i=0; i<n; i++)
    {
        cin>>cost[i]>>p[i];
        for(int j=0; j<p[i]; j++)
            cin>>a[i][j];
    }

    function<double(int)> solve = [&](int val)
    {
        if(val<=0)          return 0.0;
        if(dp[val]!=-1)     return dp[val];

        double ans=1e18;

        for(int i=0; i<n; i++)
        {
            double res = 0;
            int zeros = 0;

            for(int j=0; j<p[i]; j++)
            {
                if(a[i][j]==0)
                    zeros++;
                else
                    res += solve(val-a[i][j]);
            }

            double prob=1.0/p[i];
            res = res*prob+cost[i];

            if(zeros)
            {
                prob=1.0*p[i]/(p[i]-zeros);
                res *= prob;
            }

            ans=min(ans,res);
        }

        return dp[val] = ans;
    };

    cout<<fixed<<setprecision(9)<<solve(m);
}