Write array of arrays to TSV file

error.txt

TypeError: no implicit conversion of String into Integer

script.rb

product_urls = [["food", "citrus", "lemon"], ["food", "citrus", "lime"]] 

# write to TSV file
  CSV.open("#{product_category[0]}-#{product_category[1]}.csv", "w", "\t") do |csv|
    product_urls.each do |pu|
      csv << pu
    end
  end