#include <bits/stdc++.h>
using namespace std;

int N, A[30], B[30];

vector<vector<double>> vec(double P) {
    vector<vector<double>> ret(N, vector<double>(N));
    vector<double> tmp(1 << N);

    tmp[0] = 1;
    for (int bit = 0; bit < (1 << N); bit++) {
        int used = __builtin_popcount(bit);
        int unused = N - used;

        bool flag = true;
        for (int i = 0; i < N; i++) {
            if (~bit & (1 << i)) {
                if (flag) {
                    flag = false;
                    if (unused == 1) {
                        ret[used][i] += tmp[bit];
                    } else {
                        tmp[bit | (1 << i)] += tmp[bit] * P;
                        ret[used][i] += tmp[bit] * P;
                    }
                } else {
                    tmp[bit | (1 << i)] += tmp[bit] / (unused - 1) * (1 - P);
                    ret[used][i] += tmp[bit] / (unused - 1) * (1 - P);
                }
            }
        }
    }

    return ret;
}

int main() {
    double PA, PB;
    cin >> N >> PA >> PB;
    for (int i = 0; i < N; i++) {
        cin >> A[i];
    }
    for (int i = 0; i < N; i++) {
        cin >> B[i];
    }

    sort(A, A + N);
    sort(B, B + N);

    auto pa = vec(PA), pb = vec(PB);

    double ans = 0;
    for (int i = 0; i < N; i++) {
        for (int a = 0; a < N; a++) {
            for (int b = 0; b < N; b++) {
                if (A[a] > B[b]) {
                    ans += (A[a] + B[b]) * pa[i][a] * pb[i][b];
                }
            }
        }
    }

    cout << fixed << setprecision(10) << ans << endl;
}