For a certain exam,a score of 86 was 7 standard deviations below mean and a score of 90 was 3 standard deviations above mean.What was the mean score for the exam? Choose the correct answer:	A) 86.25	B) 84	C) 85	D) 88.8	E) 80

Rationale: "mean - 7 sd = 86 mean + 3 sd = 90 by solving above equations we get , sd ( absolute value ) = 0.4 mean = 88.8 ans . d"
Answer: D