The campus Career Center has been quite a hit. Lately they have been helping students with writing resumes, for which their 3 employees each average about 30 minutes per resume. Students have been showing up at a rate of about one every 15 minutes. 4a) What is the average time in minutes that a student can expect it to take to walk out with a completed resume after their arrival? 4b) What is the average number of students at the Career Center? 4c) What percent of the time is the Career Center empty?