Question 2:
 Budget Management Application:
Solution:
import 'dart:io';

void main() {
  print('Welcome to the Budget Management Application!');
  
  // Lists to store income and expenses
  List<Map<String, dynamic>> incomeList = [];
  List<Map<String, dynamic>> expenseList = [];
  
  // Tax rate constant
  const double taxRate = 0.15;
  
  // Main program loop
  while (true) {
    print('\nPlease choose an option:');
    print('1. Add income');
    print('2. Add expense');
    print('3. View summary');
    print('4. Exit');
    
    stdout.write('\nEnter your choice: ');
    String? choice = stdin.readLineSync();
    
    switch (choice) {
      case '1':
        // Add income
        addTransaction(incomeList, 'income');
        break;
        
      case '2':
        // Add expense
        addTransaction(expenseList, 'expense');
        break;
        
      case '3':
        // View summary
        viewSummary(incomeList, expenseList, taxRate);
        break;
        
      case '4':
        // Exit program
        print('Exiting the application. Goodbye!');
        return;
        
      default:
        print('Invalid choice! Please enter a number between 1 and 4.');
    }
  }
}

// Function to add income or expense
void addTransaction(List<Map<String, dynamic>> list, String type) {
  stdout.write('Enter ${type} description: ');
  String? description = stdin.readLineSync();
  
  while (true) {
    stdout.write('Enter ${type} amount: ');
    String? amountInput = stdin.readLineSync();
    
    try {
      double amount = double.parse(amountInput!);
      
      if (amount >= 0) {
        list.add({
          'description': description ?? 'Unknown',
          'amount': amount
        });
        
        print('${type.capitalize()} added!');
        break;
      } else {
        print('Invalid amount! Please enter a positive number.');
      }
    } catch (e) {
      print('Invalid input! Please enter a valid number.');
    }
  }
}

// Function to view summary and calculate tax
void viewSummary(List<Map<String, dynamic>> incomeList, List<Map<String, dynamic>> expenseList, double taxRate) {
  double totalIncome = calculateTotal(incomeList);
  double totalExpenses = calculateTotal(expenseList);
  double netProfit = totalIncome - totalExpenses;
  
  print('\nSummary:');
  print('Total income: \$${totalIncome.toStringAsFixed(2)}');
  print('Total expenses: \$${totalExpenses.toStringAsFixed(2)}');
  
  if (netProfit >= 0) {
    print('Net profit: \$${netProfit.toStringAsFixed(2)}');
    
    // Tax calculation using ternary operator
    double tax = netProfit > 0 ? netProfit * taxRate : 0;
    if (tax > 0) {
      print('Tax to be paid: \$${tax.toStringAsFixed(2)}');
    }
  } else {
    print('Net loss: \$${(-netProfit).toStringAsFixed(2)}');
  }
  
  // Display detailed lists
  if (incomeList.isNotEmpty) {
    print('\nIncome Details:');
    for (var income in incomeList) {
      print('- ${income['description']}: \$${income['amount'].toStringAsFixed(2)}');
    }
  }
  
  if (expenseList.isNotEmpty) {
    print('\nExpense Details:');
    for (var expense in expenseList) {
      print('- ${expense['description']}: \$${expense['amount'].toStringAsFixed(2)}');
    }
  }
}

// Function to calculate total of a list
double calculateTotal(List<Map<String, dynamic>> list) {
  double total = 0;
  for (var item in list) {
    total += item['amount'];
  }
  return total;
}

// Extension method to capitalize first letter
extension StringExtension on String {
  String capitalize() {
    return "${this[0].toUpperCase()}${this.substring(1)}";
  }
}