```ruby
# encoding: utf-8

module Cfp
  class Proposal < ActiveRecord::Base
    RANK_SCALE = (0..2).to_a
    TALK_LEVEL = %w(beginner intermediate advanced)
    LANGUAGE   = %w(English Español)

    attr_accessible :title, :abstract, :tags, :level, :language, :description

    belongs_to :user, :class_name => "::User"
    has_many :comments
    has_many :ranks

    validates :title       , :presence => true
    validates :abstract    , :presence => true
    validates :description , :presence => true

    delegate :email , :to => :user , :prefix => true
    delegate :name  , :to => :user , :prefix => true

    def self.scoped_for(user)
      case
      when user.can_review?
        scoped
      else
        user.proposals
      end
    end

    def can_be_edited_by?(user)
      Cfp::Config.cfp_open? && can_be_seen_by?(user)
    end

    def can_be_seen_by?(user)
      (self.user == user) || (user.is_admin?)
    end

    def average_ranking
      ranks.sum(:value)
    end

    def description_html
      Cfp::Proposal.renderer.render(self.description).html_safe
    end

    def abstract_html
      Cfp::Proposal.renderer.render(self.abstract).html_safe
    end

    def self.renderer
      @renderer ||= Redcarpet::Markdown.new(Redcarpet::Render::HTML,
                                             :autolink => true, :space_after_headers => true)
    end
  end
end
```

Change evaluation range to 0..5
user
```ruby
# encoding: utf-8

module Cfp
  class Proposal < ActiveRecord::Base
    RANK_SCALE = (0..5).to_a
    TALK_LEVEL = %w(beginner intermediate advanced)
    LANGUAGE   = %w(English Español)

    attr_accessible :title, :abstract, :tags, :level, :language, :description

    belongs_to :user, :class_name => "::User"
    has_many :comments
    has_many :ranks

    validates :title       , :presence => true
    validates :abstract    , :presence => true
    validates :description , :presence => true

    delegate :email , :to => :user , :prefix => true
    delegate :name  , :to => :user , :prefix => true

    def self.scoped_for(user)
      case
      when user.can_review?
        scoped
      else
        user.proposals
      end
    end

    def can_be_edited_by?(user)
      Cfp::Config.cfp_open? && can_be_seen_by?(user)
    end

    def can_be_seen_by?(user)
      (self.user == user) || (user.is_admin?)
    end

    def average_ranking
      ranks.sum(:value)
    end

    def description_html
      Cfp::Proposal.renderer.render(self.description).html_safe
    end

    def abstract_html
      Cfp::Proposal.renderer.render(self.abstract).html_safe
    end

    def self.renderer
      @renderer ||= Redcarpet::Markdown.new(Redcarpet::Render::HTML,
                                             :autolink => true, :space_after_headers => true)
    end
  end
end
```
assistant