Ahalf-life is the amount of time it takes for a substance or entity to fall to half its original value. caffeine has a half-life of about 6 hours in humans. given caffeine amount (in mg) as input, output the caffeine level after 6, 12, and 18 hours. use a string formatting expression with conversion specifiers to output the caffeine amount as floating-point numbers. ex: if the input is 100, the output is: after 6 hours: 50. mgafter 12 hours: 25. mgafter 18 hours: 12.5 mgnote: a cup of coffee has about 100 mg. a soda has about 40 mg. an "energy" drink (a misnomer) has between 100 mg and 200 mg.

// here is code in java.

import java.util.*;

class Solution

{

// main method of class

public static void main (String[] args) throws java.lang.Exception

{

   try{

    // declare variable

         double caffeine;

    // scanner object to read input from user

       Scanner scr=new Scanner(System.in);

       System.out.print("Enter the initial amount of caffeine:");

        // read the initial amount of caffeine

           caffeine=scr.nextDouble();

          // calculate amount of caffeine after 6,12,18 hours

          for(int i=1;i<=3;i++)

          {

               System.out.println("After "+ i*6+" hours:"+(caffeine/2)+" mg");

               // update the caffeine after every 6 hours

               caffeine=caffeine/2;

          }

   }catch(Exception ex){

       return;}

}

}

Explanation:

Create a variable "caffeine" to store the initial amount of caffeine given by user. Run a loop for three time, it will calculate the amount of caffeine left after every 6 hours.First it will give the amount of caffeine left after 6 hours, then caffeine left after 12 hours and in last caffeine after 18 hours.

Output:

Enter the initial amount of caffeine:100

After6 hours:50.0 mg

After12 hours:25.0 mg

After18 hours:12.5 mg

the answer is b) 2nd

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