Hello

I am very new to Ruby and currently install Ruby 1.82.15

My question, what's wrong with the following code?

class Song
	def initialize(name, artist, duration)
		@name = name
		@artist = artist
		@duration = duration
	end

	def to_s
		puts "Song: #{@name}--#{@artist} (#{@duration})"
	end
end
class KaraokeSong < Song
	def initialize(name, artist, duration, lyrics)
		super(name, artist, duration)
		@lyrics = lyrics
	end

	def to_s
		super + " [#{@lyrics}]"
	end
end
aSong = KaraokeSong.new("KSongName", "KSongArtist", 225, "Klyrics")
aSong.to_s

The error is:
Song: KSongName--KSongArtist (225)
song.rbw:33:in `to_s': undefined method `+' for nil:NilClass
(NoMethodError)
	from song.rbw:37

Please help!

Thanks in advance