An express delivery service promises overnight delivery of all packages checked in before 5 P.M. The delivery service is not perfect, however, and sometimes delays do occur. Management knows that if delays occur in the evening flight to a major city from which distribution is made, then a package will not arrive on time with probability 0.25. It is also known that 10% of the evening flights to the major city are delayed. What percentage of the packages arrive late?

(Assume that all packages are sent out on the evening flight to the major city and that all packages arrive on time if the evening flight is not delayed.)