/*

Author: Haze

2024/5/23

*/

#include <bits/stdc++.h>

#define irep(i, l, r) for(int i = (l); i <= (r); ++ i)
#define drep(i, r, l) for(int i = (r); i >= (l); -- i)
#define IOS ios::sync_with_stdio(false), cin.tie(nullptr);
using namespace std;
typedef long long ll;

inline ll readL() {
    ll s = 0;
    bool fl = false;
    char ch = (char) getchar();
    while (!isdigit(ch)) {
        if (ch == '-')fl = true;
        ch = (char) getchar();
    }
    while (isdigit(ch)) {
        s = s * 10 + (ch ^ 48);
        ch = (char) getchar();
    }
    return fl ? -s : s;
}

inline int read() {
    return (int) (readL());
}

const int mod = 1000000000 + 7;
const int itinf = 1000000999;
const ll llinf = 2e18;
const int N = 1000 + 7;

#define LD long double

LD f[2234][2234];

LD pre[2234], sqpre[2234];

void solve() {
    ll n = read(), m = read(), k = read();
    LD s, ans = 0;
    cin >> s;
    LD base = 1.0 * s * s * (1.0 * n * m / (1.0 * (m + n)));

    vector<LD>a(n + m + 1);

    irep(i, 0, n + m - 1){
        cin >> a[i + 1];
    }
    n = n + m;
    sort(a.begin() + 1, a.end());
    irep(i, 1, n){
        pre[i] = pre[i - 1] + a[i];
        sqpre[i] = sqpre[i - 1] + a[i] * a[i];
    }

    auto w = [&](int l, int r){
        return sqpre[r] - sqpre[l - 1] - (pre[r] - pre[l - 1]) * (pre[r] - pre[l - 1]) * (1.0 / (1.0 * r - l + 1));
    };
    irep(i, 0, 2050){
        irep(j, 0, 2050){
            f[i][j] = llinf;
        }
    }
    f[0][0] = 0;
    irep(i, 0, n - 1){
        irep(j, 0, k - 1){
            irep(ii, i + 1, n){
                f[ii][j + 1] = min(f[ii][j + 1], f[i][j] + w(i + 1, ii));
            }
        }
    }
    ans = f[n][1];
    irep(j, 0, k){
        ans = min(ans, f[n][j]);
    }
    cout << fixed << setprecision(12) << ans + base;
}

int main() {
    // IOS
    int T = 1;
    while (T--) {
        solve();
    }
    return 0;
}