Scores of Adults Aged 60 to 64 on a Common

Multiple Choice

Scores of adults aged 60 to 64 on a common IQ test are approximately Normally distributed with mean 90 and standard deviation 15.
About what percent of the population of adults aged 60 to 64 have an IQ lower than 60?

A) 90 percent
B) 20 percent
C) 16 percent
D) 10 percent
E) 2.5 percent