FASHION.java

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.List;
import java.util.StringTokenizer;
import java.io.IOException;
import java.io.BufferedReader;
import java.util.Collections;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.io.InputStream;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        InputReader in = new InputReader(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        FASHION solver = new FASHION();
        solver.solve(1, in, out);
        out.close();
    }

    static class FASHION {
        public void solve(int testNumber, InputReader in, PrintWriter out) {
            int testCases = in.nextInt();
            for (int i = 0; i < testCases; i++) {
                int count = in.nextInt();
                List<Integer> men = new ArrayList<>();
                List<Integer> women = new ArrayList<>();
                for (int j = 0; j < count; j++) {
                    men.add(in.nextInt());
                }
                for (int j = 0; j < count; j++) {
                    women.add(in.nextInt());
                }
                Collections.sort(men);
                Collections.sort(women);
                int ans = 0;
                for (int j = 0; j < count; j++) {
                    ans = ans + men.get(j) * women.get(j);
                }
                out.println(ans);
            }
        }

    }

    static class InputReader {
        public BufferedReader reader;
        public StringTokenizer tokenizer;

        public InputReader(InputStream stream) {
            reader = new BufferedReader(new InputStreamReader(stream), 32768);
            tokenizer = null;
        }

        public String next() {
            while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                try {
                    tokenizer = new StringTokenizer(reader.readLine());
                } catch (IOException e) {
                    throw new RuntimeException(e);
                }
            }
            return tokenizer.nextToken();
        }

        public int nextInt() {
            return Integer.parseInt(next());
        }

    }
}