A group of researchers found that people prefer training films of moderate length; shorter films contain too little information, while longer films are boring. For a training film on 36t a particular task, the researchers determined that the ratings people gave for the film could be approximated by R(t) = where t is the length of the film (in minutes) 12 + 324 Find the film length that received the highest rating The film length that received the highest rating is minutes. (Simplify your answer.)