package main

import (
	"fmt"
	"math"
	"os"
	"sort"
)

type int64Slice []int64

func (p int64Slice) Len() int           { return len(p) }
func (p int64Slice) Less(i, j int) bool { return p[i] < p[j] }
func (p int64Slice) Swap(i, j int)      { p[i], p[j] = p[j], p[i] }

func main() {
	buf := make([]byte, 65536)
	var pos, length int
	readByte := func() byte {
		if pos >= length {
			pos = 0
			n, _ := os.Stdin.Read(buf)
			if n == 0 {
				return 0
			}
			length = n
		}
		b := buf[pos]
		pos++
		return b
	}
	readInt := func() int64 {
		var b byte
		for {
			b = readByte()
			if b == 0 || b > 32 {
				break
			}
		}
		if b == 0 {
			return 0
		}
		neg := false
		if b == '-' {
			neg = true
			b = readByte()
		}
		var res int64
		for b > 32 {
			res = res*10 + int64(b-'0')
			b = readByte()
		}
		if neg {
			return -res
		}
		return res
	}

	t := int(readInt())
	for i := 0; i < t; i++ {
		n := int(readInt())
		xs := make(int64Slice, 0, n)
		ys := make(int64Slice, 0, n)
		for j := 0; j < 2*n; j++ {
			x := readInt()
			y := readInt()
			if x == 0 {
				if y < 0 {
					ys = append(ys, -y)
				} else {
					ys = append(ys, y)
				}
			} else {
				if x < 0 {
					xs = append(xs, -x)
				} else {
					xs = append(xs, x)
				}
			}
		}
		sort.Sort(xs)
		sort.Sort(ys)

		var ans float64
		for j := 0; j < n; j++ {
			ans += math.Sqrt(float64(xs[j]*xs[j] + ys[j]*ys[j]))
		}
		fmt.Printf("%.15f\n", ans)
	}
}