Ruby solution to conversion of text into a phone number

text2number.rb

def n2t(text)
  letters = ["a","b","c","d","e","f","g","h","i","j","k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z"," "]
  numbers = [ 2 , 2,  2 , 3 , 3 , 3 , 4 , 4 , 4 , 5 , 5 , 5 , 6 , 6 , 6 , 7 , 7 , 7 , 7 , 8 , 8 , 8 , 9 , 9 , 9 , 9 , 0 ]
  output = String.new()
  
  for ti in 0..text.length
    for li in 0..letters.length
      if letters[li] == text[ti] then
        output << numbers[li].to_s
      end
    end
  end
  print output
end