Question 17
Some overlapping circles divide the plane into several regions. Numbers are filled in these areas such that for any pair of overlapping circles, say A and B, the number in the intersection area of circle A and B is the average of the two numbers in the areas solely in A or B. For example, the figure on the right shows $\frac{1+5}2=3$ , $\frac{5+11}2=8$ and $\frac{11+13}2=12$ . In the figure below, there are five overlapping circles and ten numbers are filled according to the conditions above. What is the sum of the numbers a and b?
