class Rubycritic::Rating

def self.from_cost(cost)
  if    cost <= 2  then new("A")
  elsif cost <= 4  then new("B")
  elsif cost <= 8  then new("C")
  elsif cost <= 16 then new("D")
  else new("F")
  end
end

def initialize(letter)
  @letter = letter
end

def to_s
  @letter
end