I have three errands to take care of in the Administration Building. Let X, the time that it takes for the ith errand (i=1, 2, 3), and let X the total time in minutes that I spend walking to and from the building and between each errand. Suppose the X's are independent, and normally dis- tributed, with the following means and standard deviations: = 15, = 4,2 5,02 =1, z=8, = 2, = 12, 4=3. I plan to leave my office at precisely 10:00 A.M. and wish to post a note on my door that reads, "I will return by t A.M." What time t should I write down if I want the proba- bility of my arriving after t to be .01?