Two cars start simultaneously from towns Alpha and Beta, which are 30 miles apart along a straight road, and drive towards each other. The road is divided into three 10-mile sections. For a car traveling from Alpha to Beta, the speed limit is 30 mph in the first section, 20 mph in the second section, and 10 mph in the third section. Both cars travel exactly at the speed limit for the section they are in. How many miles from town Alpha do they meet?