# File library_solution.rb, line 71
                def get_link(isbn)
                        doc = get_avail(isbn, :isbn)
                        rn = doc.root.elements['t'].attribute('rn')
                        if rn.nil?
                                return nil
                        else
                                ac = tc = 0
                                doc.elements.each("r/t/lo") { |lo| ac += lo.attributes.get_attribute('ac').value.to_i ; tc += lo.attributes.get_attribute('tc').value.to_i }
                                return "<a href=\"http://#{@web_server_address}#{@detail_url}#{rn.to_s}\">#{ac} of #{tc} available</a>"
                        end
                end