The average ages (in years) of persons in groups A, B and C are 37, 23 and 41 years, respectively. If the average age of persons in groups A and B combined is 29, that of B and C is 33 and that of A and C is 39.5, then the average age of all the persons combined in these three groups is∶

• A. 35.8
• B. 34.8
• C. 34
• D. 33