import java.text.DecimalFormat;
import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner scanner = new Scanner(System.in);
int n = scanner.nextInt();
for (int i = 0; i < n; i++) {
double h = scanner.nextDouble();
int t = scanner.nextInt();
//题意: 计算从小球H 高度下落到第n 次弹地往返的总路程
double sum =0;
for (int j = 0; j < t-1; j++) {
sum+=h*1.5;
h/=2;
}
sum+=h;
DecimalFormat f = new DecimalFormat("0.00");
System.out.println(f.format(sum));
}
}
}