The Stanford-Binet IQ scores of a group of people are normally distributed with the mean of 100 and a standard deviation of 16. According to this test, what is the probability tha a randomly selected member of the group will have the following IQ?

a) an IQ less than 100

b) an IQ greater than 116

c) an IQ less than 116

d) an IQ between 84 and 116

100 -16 = 84 and 100 + 16 = 116

84<=x<=116 would be the first standard deviation

how do I calculate the probabilities ?