The Decrease in Cholesterol Level After Eating a Certain Brand

The decrease in cholesterol level after eating a certain brand of oatmeal for breakfast for one month in people with cholesterol levels more than 200 mg/dl is Normally distributed, with mean (in milligrams, mg) μ and standard deviation σ= 3. The brand advertises that eating its oatmeal for breakfast daily for one month will produce a mean decrease in cholesterol of more than 10 points for people with cholesterol levels more than 200 mg/dl, but you believe that the mean decrease in cholesterol is less than advertised. To explore this question, you test the following hypotheses:
H₀: μ= 10, H_a: μ< 10
You carry out the test at a significance level of 0.05 by randomly selecting 100 people with cholesterol levels more than 200 mg/dl and, after they have eaten this brand of oatmeal for one month, computing the mean decrease x̄ in the subjects' cholesterol levels. What is the probability of a Type I error for your test at μ= 8.5?

A) 0.0012
B) 0.0500
C) 0.9500
D) 0.9988