A work sampling study was conducted to determine the proportion of the time a worker is idle. The following information was gathered on a random basis: Day Monday Tuesday Wednesday Thursday Number of Times Worker Idle 10 13 15 17 Total Number of Observations 41 57 45 52 a. Based on these preliminary results, what percent of the time is the worker working? The worker is working % of the time. (Enter your response rounded to two decimal places.) b. If idle time is judged to be excessive, what additional categories might you add to a follow-up work sampling study to identify the root causes? (Mark all that apply.) O A. Waiting for a customer order OB. Performance of workers C. Equipment failures OD. Number of workers