#include <iostream>
#include <iomanip> 
#include <vector>
#include <cmath>

using namespace std;

const int N = 1e5 + 10;

int n;
double price, r;
int head[N], p[N], s[N], d[N];
vector<int> vec;
double res;

void dfs(int r)//遍历树，求零售商到根节点的距离
{
    for(int i = head[r]; i != -1; i = p[i])
    {
        d[i] = 1 + d[r];
        dfs(i);
    }
}

int main()
{
    cin >> n >> price >> r;

    for (int i = 0; i < n; i++)
        head[i] = -1;

    for (int i = 0; i < n; i++)
    {
        int t;
        cin >> t;

        if(t == 0)
        {
            int a;
            cin >> a;
            vec.push_back(i);//保存零售商的编号
            s[i] = a;//保存零售商售卖产品数量
        }

        else
        {
            for(int j = 0; j < t; j++)
            {
                int b;
                cin >> b;
                p[b] = head[i];
                head[i] = b;
            }
        }
    }

    dfs(0);

    for(int i = 0; i < vec.size(); i++)
        res += s[vec[i]] * price * pow(1 + r / 100, d[vec[i]]);

    // 使用fixed和setprecision设置输出格式
    cout << fixed << setprecision(1) << res << endl;

    return 0;
}