The average (arithmetic mean) of a normal distribution of a school's test scores is 65, and standard deviation of the distribution is 6.5. A student scoring a 78 on the exam is in what percentile of the school?

A) 63rd percentile
B) 68th percentile
C) 84th percentile
D) 96th percentile
E) 98th percentile

OA is E
Can an Expert give a mathematical approach to solve this question? Thanks