Sampling Distribution Question

Also having some trouble with this one:

**Suppose we assume that the temperatures of healthy humans is approximately normal with a mean of 98.6 degrees and a standard deviation of 0.8 degrees. **

*(a) If 130 people are selected at random, what is the probability that the average temperature for these people is 98.25 degrees or lower?*

(b) Would you consider an average temperature of 98.25 degrees to be an unlikely occurrence, given that the true average temperature of healthy people os 98.6 degrees. Explain

The answers:

(a) ≈0

(b) Yes; the mean value is 98.25, which is almost 5 standard deviations below the assumed mean of 98.6

Any help will be greatly appreciated, as i am interested in how these answers are obtained.