Untitled

What convention should I use for instance variables?
class BookInStock
  attr_reader: isbn
  attr_accessor: price

  def initialize (isbn, price)
    @isbn = isbn
    @price = Float (price)
  end

  def price_in_cents
    Integer (price * 100 + 0.5)
  end
end

class BookStock

  def set_price (price)
    @price = price
  end

  def get_price
    @price
  end
end

class Person
  attr_reader :name

  def initialize(name)
    @name = name
  end

  def blank?
    !@name
  end

  def to_s
    name
  end
end

class Person
  def initialize(first_name, last_name)
    @first_name, @last_name = first_name, last_name
  end

  def name
    "#{@first_name} #{@last_name}"
  end

  def blank?
    !@first_name and !@last_name
  end

  def to_s
    name
  end
end