How can I generate code for this problem

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C#

create a C# application that calculate and displays membership fees for N customers who registered for membership
Length of MembershipRate(including tax)
1-8weeks $40.0per
week8-16weeks $35.5per week
More than 16weeks $25.0per week

the application should ask the user to enter the customer name, the number of months for membership, and yes or no to indicate whether the customer receives a special offer or not. The special offer will give customers a 20% discount of the membership no matter how many weeks they register. Assume that the number of week to be entered is an integer type with the range between 1 and 30. An error message should be issued if a user enters a value beyond this range and the re-entering is required.The program makes a calculation of membership and displays the result as shown in the below figure. The program should be kept running with entering next set of input data

What I have tried:

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace GymMembership
{
public class exercise18
{
static void Main(string[] args)
{
int weeks;
bool specialOffer;
double discount = 20 , totalAmount = 0;
string name;

Console.Write("\n\n");
Console.Write("Calculate membership fees:\n");
Console.Write("----------------------------");
Console.Write("\n\n");

Console.Write("Input number of weeks :");
weeks = Convert.ToInt32(Console.ReadLine());
Console.Write("Input the name of the customer :");
name = Console.ReadLine();
Console.Write("Input the special offer by the customer : ");
specialOffer = Convert.ToBoolean(Console.ReadLine());
if (weeks <= 8)
totalAmount = (((40.0 * weeks) * discount / 100) - (40.0 * weeks));
else if (weeks > 8)
totalAmount = (((35.5 * weeks) * discount / 100) - (35.5 * weeks));
else if (weeks > 16)
totalAmount = (((25.0 * weeks) * discount / 100) - (25.0 * weeks));
else (weeks > 30){
Console.WriteLine("error");
}
Console.Write("\nElectricity Bill\n");
Console.Write("Customer IDNO :{0}\n", weeks);
Console.Write("Customer Name :{0}\n", name);
Console.Write("special offer :{0}\n", specialOffer);
Console.Write("discount Amount :{0}\n", discount);
Console.Write("Net Amount Paid By the Customer :{0}\n", totalAmount);
}
}
}