Exercise 3.1 There a four companies (A, B, C, D) in a town that deliver packages. Com- pany A delivers 40% of all the packages. Company B delivers 30% of all the packages. Company C delivers 20% of all the packages. Company D delivers 10% of all the pack- ages. Company A delivers 90% of its packages on time. Company B delivers 95% of its packages on time. Company C delivers 85% of its packages on time. Company D delivers 80% of its packages on time. You order a package. What is the probability that it arrives on time?