import java.util.*;
import java.io.*;

public class raffle_verf {

	public static void main(String[] args) throws FileNotFoundException{
		Scanner scan = new Scanner(new File("raffle.in"));
		PrintWriter out = new PrintWriter(new File("raffle_verf.out"));
		int t = scan.nextInt();
		for(int q = 1; q <= t; q++){
			int n = scan.nextInt();
			int b = scan.nextInt();
			if(!(n >= 1 && n <= 100)) problem(q);
			if(!(b >= 1 && b <= n)) problem(q);
			double[] arr = new double[n];
			for(int i = 0; i < n; i++){
				int v = scan.nextInt();
				int d = scan.nextInt();
				if(!(v >= 1 && v <= 10000)) problem(q);
				if(!(d >= 0 && d <= 10000)) problem(q);
				arr[i] = v/(double)(d+1);
			}
			Arrays.sort(arr);
			double ans = 0;
			for(int i = n-1; i >= n-b; i--)
				ans += arr[i];
			out.printf("%.2f\n", ans);
		}
		out.flush();
	}

	static void problem(int caseID){
		System.out.println("Issue with case "+caseID);
	}
}