question_answer

Amole was asked to calculate the arithmetic mean of ten positive integers each of which had two digits. By mistake, he interchanged the two digits, say a and b, in one of these ten integers. As a result, his answer for the arithmetic mean was 1.8 more than what it should have been. Then b - a equals

A)  1                    

B)  2       

C)  3                    

D)  None of these