text: def aumentar(preco=0, taxa=0, formato=False):
      v = preco + (preco * taxa / 100)
      return v if format is False else moeda(v)
  
  
  def diminuir(preco=0, taxa=0, formato=False):
      v = preco - (preco * taxa / 100)
      return v if format is False else moeda(v)
  
  
  def dobro(preco=0, formato=False):
      v = preco * 2
      return v if format is False else moeda(v)
  
  
  def metade(preco=0, formato=False):
      v = preco / 2
      return v if format is False else moeda(v)
  
  
  def moeda(preco=0, moeda='R$'):
      return f'{moeda}{preco:8.2f}'.replace('.', ',')