You have an important document that has to be delivered to your Detroit office tomorrow morning. You call a number of overnight delivery services and fnd that each one claims an 80% probability that it can deliver your document on time. Concerned about your future with the frm, you decide to select TWO of the services, each of which will be given a copy of the document to deliver. Construct a probability tree to answer the following questions:

a. How likely is it that your Detroit office will receive the document in time?

b. Still nervous, you decide to go with THREE services. Now how likely is it that the Detroit office receives what it needs tomorrow morning?

c. How many services should you use if you want to allow no more than 1 chance in a thousand that the document will not be received in time?