package main

import (
	"bufio"
	"fmt"
	"os"
	"sort"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	out := bufio.NewWriter(os.Stdout)
	defer out.Flush()

	var t int
	if _, err := fmt.Fscan(in, &t); err != nil {
		return
	}
	for ; t > 0; t-- {
		var n int
		fmt.Fscan(in, &n)
		m := 2 * n
		a := make([]int, m)
		for i := 0; i < m; i++ {
			fmt.Fscan(in, &a[i])
		}
		sort.Ints(a)
		var sum int64
		for i := 0; i < m; i += 2 {
			sum += int64(a[i])
		}
		fmt.Fprintln(out, sum)
	}
}