The average of 18 observations was calculated and it was 124. Later on it was discovered that two observations 46 and 82 were incorrect. The correct values are 64 and 28. The correct average of 18 observations is___________?

A. 123
B. 137
C. 121
D. 122

Sum of 18 observations = 18×124 =2232

Correct sum of 18 observations = 2232-46-82+64+28

= 2196

Therefore, Correct average =2196/18 = 122