There are two towns, conveniently called ``A'' and ``B'' joined by a road. A businesswoman must drive from A to B, conduct some business (what else?) and return to A. She wants her total round trip speed to average 60 miles per hour, but she encountered heavy traffic going to B and averaged only 30 miles per hour on the first half of the trip. What should her average speed be on the return trip to meet her goal?