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#include <vector>
#include <map>
#include <set>
#include <queue>
#include <cassert>
#include <algorithm>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <ctime>
using namespace std;
#define DB(x) { cerr << #x << ": " << x << " "; }
#define forn(i, n)  for (int i = 0; i < (int)(n); ++i)
#define sqr(x) ((x)*(x))
typedef long double ld;
typedef long long ll;
typedef vector <int> vi;
typedef pair <int,int> pii;
const ld PI = acos(-1.0);

const int N = 1010;
int n, k;
double prices[N], disc[N], c[N][N];

void precalc() {
    forn(i, N) {
        c[i][0] = c[i][i] = 1;
        for (int j = 1; j < i; j++)
            c[i][j] = c[i - 1][j - 1] + c[i - 1][j];
    }
}

void solve() {
    cin >> n >> k;
    forn(i, n) cin >> prices[i];
    sort(prices, prices + n);
    forn(i, k) cin >> disc[i];
    sort(disc, disc + k);
    double res = 0;
    forn(i, n) forn(j, k) {
        if (j > i) continue;
        if (k - j > n - i) continue;
        double add = c[i][j] * c[n - i - 1][k - j - 1] * disc[j] * prices[i];
        res += add;
        //cerr << i << " " << j << " " << add << endl;
    }
    res /= c[n][k] * 100;
    cout << fixed << setprecision(3) << res << endl;
}

int main() {
  //freopen("in", "r", stdin);
  //freopen("out", "w", stdout);
  ios_base::sync_with_stdio(0);

    precalc();
    int T; cin >> T; forn(t, T) solve();
  return 0;
}