Last year the avg. salary of the 10 employees of Company X was $42,800. What is the avg. salary of the same 10 employees this year?
1) For 8 of the 10 employees, this year's salary is 15 percent greater than last year's salary.
2) For 2 of the 10 employees, this year's salary is the same as last year's salary








Sum = Avg * data points
Note - the SUM of the salaries will answer the data sufficiency problem just as well as the AVERAGE that's explicitly requested.

I believe it is E because given (1) and (2) together, we have no way of knowing the individual salaries and we cannot assume that the individual salaries are each equal to the previous year's average. For example, perhaps the highest 8 salaries increased by 15% and the lowest 2 did not change at all, the average would surely be different than if the highest 2 salaries did not change and the other 8 increased by 15%.

Ans - E