Ventaz corp manufactures small windows for back yard sheds. historically, its demand has ranged from 30 to 50 windows per day with an average of 42. alex is the one production worker and he works eight hours a day, five days a week. each order is one window and each window takes 5 minutes. alex plans to add doors to its product line and anticipates that they will average 4 doors per day. each door takes 540 minutes to install. what is the average waiting time, in minutes, if alex continues to be the only worker?