Answer: 21.9
Step-by-step explanation: To find the length of boundary ABCD, we add the lengths of each line segment and the two arcs. AB is 5, BC is (120/360) * 2 * pi * 5 = 10pi/3, CD is 5, and DA is (30/360) * 2 * pi * 5 = pi/3. Adding these lengths, we get (20pi + 15)/3, which is approximately 21.9 when rounded to one decimal place.
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