Excerise from Upcase: https://exercises.upcase.com/exercises/replace-variable-with-query

tipper.rb

class Tipper
  TAX = 0.05
  
  def initializer(amount:, discount_percentage: 0, tip_percentage:)
    @amount = amount
    @discount_percentage = discount_percentage
    @tip_percentage = tip_percentage
  end
  
  def total
    amount + tax_amount - discount_amount + tip_amount
  end
  
  private
  
  def tax_amount
    amount + TAX
  end
  
  def discount_amount
    amount * (discount_percentage / 100.0)
  end
  
  def tip_amount
    amount * (tip_percentage / 100.0)
  end
  
  attr_reader :amount, :discount_percentage, :tip_percentage
end